Methods for culturing filamentous fungi in fermentation media

ABSTRACT

Methods for culturing filamentous fungi, in which the filamentous fungi are grown in a colloid of air and a fermentation medium, are provided. The methods result in more rapid and prolific growth of the filamentous fungus than has been achieved by previous methods. Biomats produced by the methods and air-medium colloids for use in the methods are also provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.17/117,715, filed 10 Dec. 2020, which claims the benefit of U.S.Provisional Patent Application 62/946,404, filed 10 December 2019, theentireties of both of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to methods for culturingfilamentous fungi, and particularly to methods in which a filamentousfungus is cultured in or on a colloid of a growth medium and air oranother user-defined atmosphere, e.g. an atmosphere with a controlledcontent of oxygen or other constituents to promote fungal growth.

BACKGROUND OF THE INVENTION

The use of filamentous fungi as valuable microbial factories has beenexploited in the past, but has generally required significantinfrastructure and/or equipment, energy requirements, expensivereagents, and/or significant human resources. Filamentous fungi arewell-known for having the greatest metabolic diversity of allmicroorganisms on Earth, including the ability to produce a widespectrum of organic acids, enzymes, hormones, lipids, mycotoxins,vitamins, pigments, recombinant heterologous proteins, and other smallmolecules of interest (e.g. medicinal compounds such as antibiotics,antifungals, and anti-cancer drugs), as well as the ability to degrademany types of recalcitrant materials such as lignocellulose and humicsubstances in soils.

While widely used, significant challenges to production by submergedfermentation still exist and include important factors such as growthlimitation due to the restricted oxygen availability and excessive shearforces generated by agitation. Because oxygen solubility in water istypically about 8 milligrams per liter, oxygen is readily depletedduring rapid growth in submerged cultures. Thus, continuous aerationusing complex, expensive, and energy-intensive aeration and agitationsystems is required to maintain high growth rates. The cultivation offilamentous fungi is even more challenging because the filamentousmorphology imparts non-Newtonian rheological behavior that furtherinhibits oxygen transfer in solution. As culture densities increase, theamount of energy required to aerate and mix the cultures increasesnonlinearly, and the energy requirements to aerate dense cultures arethus very high. For many filamentous species, vigorous agitation andaeration of the cultures becomes detrimental to hyphal growth and as aresult dramatically decreases growth rates. These and other challengesto submerged fermentation of filamentous microorganisms requireinnovative solutions to effectively harness the benefits of theseorganisms in application where resources are limited, e.g. aboardspacecraft or space stations or in challenging terrestrial environments.

More recently, some significant strides have been made in thedevelopment of systems and methods for culturing filamentous fungi thatdo not require active aeration or agitation of the liquid culture,particularly to produce biomats with significant tensile strength.However, the availability of oxygen to the fungus can still present achallenge even in these newer methods and systems. In addition, withoutwishing to be bound by any particular theory, it is believed that thesurface area of the fungus/feedstock interface may also be a limitingfactor in the growth of filamentous fungi in these applications.

There is thus a need in the art for systems and methods for culturingfilamentous fungi in fermentation media that overcomes these and otherdrawbacks of submerged fermentation. It is further advantageous for suchsystems and methods to provide the fungus with greater oxygenavailability and/or surface area in contact with a feedstock thanprevious systems and methods.

SUMMARY OF THE INVENTION

It is one aspect of the present invention to provide a method forculturing a filamentous fungus in a fermentation medium, comprising (a)aerating the fermentation medium to provide an air-medium colloid (AMC);and (b) culturing the filamentous fungus in or on the AMC to form abiomass of the filamentous fungus.

In embodiments, the AMC may be used as a self-contained bioreactorsystem that isolates the filamentous fungus from a surroundingenvironment, thus providing a fungal growth system that does not requireenvironmental control.

In embodiments, the AMC may comprise a gelation agent, a viscositymodifier, and/or a humectant or other water activity-reducing component.

In embodiments, the AMC may comprise an inoculum of the filamentousfungus.

In embodiments, the method may further comprise inoculating the AMC withan inoculum of the filamentous fungus.

In embodiments, the AMC may comprise a stabilizer. The stabilizer may,but need not, comprise xanthan gum. A mass ratio of the fermentationmedium to the stabilizer in the AMC may, but need not, be between about100:1 and about 1,000:1. The stabilizer may, but need not, be selectedfrom the group consisting of polysaccharide gums (e.g. xanthan gum, guargum, locust bean gum, konj ac root gum), anionic surfactants (e.g.carboxylates, phosphate esters, sulfate esters, sulfonate esters),cationic surfactants (e.g. primary, secondary, or tertiary amines,quaternary ammonium salts), ceteareth 20, cellulose, diacetyl tartaricesters of mono- and diglycerides (DATEM), diglycerides, emulsifying wax,glycerol monostearate, lecithins, monoglycerides, mustards, non-ionicsurfactants (e.g. polysorbate 20, polysorbate 80), soaps, sodiumphosphates, sodium stearoyl lactylate, zwitterionic surfactants,saponins, starches, modified starches, plant protein surfactants (e.g.soy protein isolate, pea protein isolate), animal protein surfactants(e.g. casein, whey protein isolate), microparticulates, silica, andcombinations and mixtures thereof.

In embodiments, a volume fraction of air in the AMC may be between about0.05 and about 0.95, between about 0.1 and about 0.9, between about 0.2and about 0.8, between about 0.3 and about 0.7, between about 0.4 andabout 0.6, or about 0.5.

In embodiments, the AMC may be a foam that is stable over at least about1 day, at least about 2 days, at least about 3 days, at least about 4days, at least about 5 days, at least about 6 days, at least about 7days, at least about 8 days, at least about 9 days, at least about 10days, at least about 11 days, at least about 12 days, at least about 13days, at least about 14 days, at least about 15 days, at least about 16days, at least about 17 days, at least about 18 days, at least about 19days, at least about 20 days, at least about 21 days, at least about 22days, at least about 23 days, at least about 24 days, at least about 25days, at least about 26 days, at least about 27 days, at least about 28days, at least about 29 days, or at least about 30 days.

In embodiments, the filamentous fungus may belong to an order selectedfrom the group consisting of Ustilaginales, Russulales, Polyporales,Agaricales, Pezizales, and Hypocreales.

In embodiments, the filamentous fungus may belong to a family selectedfrom the group consisting of Ustilaginaceae, Hericiaceae, Polyporaceae,Grifolaceae, Lyophyllaceae, Strophariaceae, Lycoperdaceae, Agaricaceae,Pleurotaceae, Physalacriaceae, Omphalotaceae, Tuberaceae, Morchellaceae,Sparassidaceae, Nectriaceae, and Cordycipitaceae.

In embodiments, the filamentous fungus may belong to a species selectedfrom the group consisting of Ustilago esculenta, Hericulum erinaceus,Polyporous squamosus, Grifola fondosa, Hypsizygus marmoreus, Hypsizygusulmarius, Calocybe gambosa, Pholiota nameko, Calvatia gigantea, Agaricusbisporus, Stropharia rugosoannulata, Hypholoma lateritium, Pleurotuseryngii, Pleurotus ostreatus, Tuber borchii, Morchella esculenta,Morchella conica, Morchella importuna, Sparassis crispa, Fusariumvenenatum, MK7 ATCC Accession Deposit No. PTA-10698, Disciotis venosa,and Cordyceps militaris.

In embodiments, the method may further comprise, prior to or during step(b), adding a food-grade or food-safe additive to the AMC.

It is another aspect of the present invention to provide a filamentousfungal biomat, produced by a method as described herein.

In embodiments, the biomat may have at least one of the followingproperties: (a) a thickness of at least about 1.75 mm; (b) a mass of atleast about 295 grams per square meter of a top surface area of the AMC;(c) a dry density of at least about 0.20 g/cm³; (d) a tensile strengthof at least about 255 kPa; and (e) a carbohydrate content of at leastabout 47 wt % when dry.

It is another aspect of the present invention to provide a filamentousfungal biomat, having at least one of the following properties: (a) athickness of at least about 1.75 mm; (b) a mass of at least about 295grams per square meter of a top surface area of the AMC; (c) a drydensity of at least about 0.20 g/cm³; (d) a tensile strength of at leastabout 255 kPa; and (e) a carbohydrate content of at least about 47 wt %when dry.

In embodiments, a biomat as described herein may comprise a stabilizer.

In embodiments, a biomat as described herein may comprise a food-gradeor food-safe additive.

It is another aspect of the present invention to provide a foodstuff,comprising at least a portion of a biomat as described herein.

It is another aspect of the present invention to provide a structuralmaterial, comprising at least a portion of a biomat as described herein.

It is another aspect of the present invention to provide a textilematerial, comprising at least a portion of a biomat as described herein.

It is another aspect of the present invention to provide an air-mediumcolloid (AMC), comprising a fermentation medium; and air, colloidallydispersed throughout the fermentation medium.

In embodiments, the AMC may further comprise a stabilizer.

For purposes of further disclosure and to comply with applicable writtendescription and enablement requirements, the following references areincorporated herein by reference in their entireties:

-   Elka S. Basheva et al., “Unique properties of bubbles and foam films    stabilized by HFBII hydrophobin,” 27(6) Langmuir 2382 (February    2011).-   Graeme P. Boswell and Fordyce A. Davidson, “Modelling hyphal    networks,” 26(1) Fungal Biology Reviews 30 (April 2012).-   Andrew R. Cox et al., “Exceptional stability of food foams using    class II hydrophobin HFBII,” 23(2) Food Hydrocolloids 366 (March    2009).-   Monika S. Fischer and N. Louise Glass, “Communicate and fuse: how    filamentous fungi establish and maintain an interconnected mycelial    network,” 10 Frontiers in Microbiology 619 (March 2019).-   Luke Heaton et al., “Analysis of fungal networks,” 26(1) Fungal    Biology Reviews 12 (April 2012).

While specific embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise configuration and componentsdescribed herein. Various modifications, changes, and variations whichwill be apparent to those skilled in the art may be made in thearrangement, operation, and details of the methods and systems of thepresent invention disclosed herein without departing from the spirit andscope of the invention. It is important, therefore, that the claims beregarded as including any such equivalent construction insofar as theydo not depart from the spirit and scope of the present invention.

The advantages of the present invention will be apparent from thedisclosure contained herein.

As used herein, “at least one,” “one or more,” and “and/or” areopen-ended expressions that are both conjunctive and disjunctive inoperation. For example, each of the expressions “at least one of A, B,and C,” “at least one of A, B, or C,” “one or more of A, B, and C,” “oneor more of A, B, or C,” and “A, B, and/or C” means A alone, B alone, Calone, A and B together, A and C together, B and C together, or A, B,and C together.

It is to be noted that the term “a” or “an” entity refers to one or moreof that entity. As such, the terms “a” (or “an”), “one or more,” and “atleast one” can be used interchangeably herein. It is also to be notedthat the terms “comprising,” “including,” and “having” can be usedinterchangeably.

The embodiments and configurations described herein are neither completenor exhaustive. As will be appreciated, other embodiments of theinvention are possible utilizing, alone or in combination, one or moreof the features set forth above or described in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates four samples of filamentous fungus grown on anair-medium colloid (AMC), according to embodiments of the presentinvention, and two samples of filamentous fungus grown on anon-colloidal growth medium.

FIG. 2 illustrates two trays in which filamentous fungus was grown on anAMC, according to embodiments of the present invention, and one tray inwhich filamentous fungus was grown on a standard non-emulsified growthmedium.

FIG. 3 is a graph of comparative growth for conventional surfacefermentations and AMC fermentations.

FIGS. 4 and 5 are protein assays of surface-fermented and AMC-fermentedfungal specimens, respectively.

FIGS. 6A and 6B are top and bottom views, respectively, of a meshsubstrate before harvesting of fungal biomats grown thereon.

FIG. 7 is a view of the mesh substrate of FIGS. 6A and 6B after biomatharvesting.

FIG. 8 is a graph showing the effect of carbon concentration and/orcarbon-to-nitrogen ratio, in both AMCs and conventional liquid surfacefermentation (LSF) media, on biomat thickness.

FIG. 9 is a graph showing the effect of carbon concentration and/orcarbon-to-nitrogen ratio, in both AMCs and conventional LSF media, onbiomat area yield.

FIG. 10 is a graph showing the effect of carbon concentration and/orcarbon-to-nitrogen ratio, in both AMCs and conventional LSF media, onbiomat density.

FIG. 11 is a graph showing the effect of carbon concentration and/orcarbon-to-nitrogen ratio, in both AMCs and conventional LSF media, onbiomat tensile strength.

FIG. 12 is a graph showing the effect of carbon concentration and/orcarbon-to-nitrogen ratio, in both AMCs and conventional LSF media, onbiomat strain at break.

FIGS. 13A through 13D are graphs showing the effect of carbonconcentration and/or carbon-to-nitrogen ratio, in both AMCs andconventional LSF media, on biomat ash, carbohydrate, fat, and proteincontent, respectively.

FIG. 14 is a graph showing the effect of mixing technique/device used toprepare AMCs on biomat thickness.

FIGS. 15A and 15B are graphs showing the effect of mixingtechnique/device used to prepare AMCs on biomat area yield and density,respectively.

FIG. 16 is a graph showing the effect of mixing technique/device used toprepare AMCs on biomat tensile strength.

FIG. 17 is a graph showing the effect of mixing technique/device used toprepare AMCs on biomat strain at break.

FIG. 18 is a graph showing the effect of AMC thickener on biomatthickness.

FIGS. 19A and 19B are graphs showing the effect of AMC thickener onbiomat area yield and density, respectively.

FIG. 20 is a graph showing the effect of AMC thickener on biomat tensilestrength.

FIG. 21 is a graph showing the effect of AMC thickener on biomat strainat break.

FIG. 22A is a light microscopy image at 40× magnification of a 5 μmcross-section of a biomat grown on a conventional liquid surfacefermentation medium containing 15 wt % fructose.

FIGS. 22B, 22C, and 22D are light microscopy images at 100×magnification of bottom (medium-side), middle, and top (hyphal-side)sections of a 5 μm cross-section of a biomat grown on a conventionalliquid surface fermentation medium containing 15 wt % fructose.

FIG. 23A is a light microscopy image at 40× magnification of a 5 μmcross-section of a biomat grown on an AMC medium containing 15 wt %fructose.

FIGS. 23B, 23C, and 23D are light microscopy images at 100×magnification of bottom (medium-side), middle, and top (hyphal-side)sections of a 5 μm cross-section of a biomat grown on an AMC mediumcontaining 15 wt % fructose.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “biomass” refers to a filamentous fungalstructure formed from mycelial growth in an interwoven or intermeshedmanner to produce filamentous fungal mass that is coherent.

As used herein, the term “biomat” refers to a filamentous fungalstructure having a significantly uniform thickness and a relativelylarge surface area-to-thickness ratio.

As used herein, unless otherwise specified, the term “colloid” refers toa mixture in which particles of one substance (the “dispersed phase”)are dispersed throughout a volume of a different substance (the“dispersion medium”), for example the dispersed phase can comprise orconsist of microscopic bubbles, particles, etc. Where the dispersedphase and the dispersion medium of a colloid are specifically identifiedherein, they are separated by a hyphen, with the dispersed phaseidentified first, e.g. a reference herein to an “air-medium colloid”refers to a colloid in which air is the dispersed phase and a medium(e.g. a fermentation medium or growth medium) is the dispersion medium.

As used herein, unless otherwise specified, the term “emulsion” refersto a colloid in which both the dispersed phase and the dispersion mediumare liquids. Examples of emulsions as that term is used herein includebut are not limited to latex, lotion, mayonnaise, and the fat fractionof milk.

As used herein, unless otherwise specified, the term “foam” refers to acolloid in which the dispersed phase is a gas and the dispersion mediumis a liquid. Examples of foams as that term is used herein include butare not limited to shaving cream and whipped cream.

As used herein, unless otherwise specified, the term “gel” refers to acolloid in which the dispersed phase is a liquid and the dispersionmedium is a solid. Examples of gels as that term is used herein includebut are not limited to agar, gelatin, and jelly. In embodiments of thepresent invention, AMCs in the form of polysaccharide gels may beprepared by, e.g., divalent and monovalent ionic crosslinking,self-assembly, fiber alignment, covalent crosslinking, non-ioniccrosslinking, and/or solvent removal crosslinking. AMC gels may bedried, in some embodiments freeze-dried, for storage or transport andthen rehydrated for later use.

As used herein, unless otherwise specified, the term “liquid aerosol”refers to a colloid in which the dispersed phase is a liquid and thedispersion medium is a gas. Examples of liquid aerosols as that term isused herein include but are not limited to clouds, condensation, fog,hair spray, and mist.

As used herein, unless otherwise specified, the term “sol” refers to acolloid in which the dispersed phase is a solid and the dispersionmedium is a liquid. Examples of sols as that term is used herein includebut are not limited to blood, pigmented ink, and the protein fraction ofmilk.

As used herein, unless otherwise specified, the term “solid aerosol”refers to a colloid in which the dispersed phase is a solid and thedispersion medium is a gas. Examples of solid aerosols as that term isused herein include but are not limited to atmospheric particulates, iceclouds, and smoke.

As used herein, unless otherwise specified, the term “solid foam” refersto a colloid in which the dispersed phase is a gas and the dispersionmedium is a solid. Examples of solid foams as that term is used hereininclude but are not limited to aerogel, pumice, and Styrofoam.

As used herein, unless otherwise specified, the term “solid sol” refersto a colloid in which both the dispersed phase and the dispersion mediumare solids. Examples of solid sols as that term is used herein includebut are not limited to cranberry glass.

As used herein, unless otherwise specified, the term “stability” refersto the proportion of an initial volume of a foam that is retained by thefoam after a specified interval. By way of non-limiting example, a foamthat has an initial volume of five liters and a volume of four liters 14days later thus has 80% stability over 14 days. Unless otherwisespecified, a “stable” foam, as that term is used herein, is a foam thathas at least 50% stability after a specified interval.

The present invention provides for rapid and prolific growth offilamentous fungi by culturing a filamentous fungus on or in anair-medium colloid (AMC), in which air is dispersed within afermentation medium or growth medium. Typically, the AMC is providedwith a stabilizer to improve the foam stability of the AMC and thuspreserve the increased volume of the AMC over a longer period. Inembodiments, the AMC is formed by aerating the fermentation medium, andmay optionally include other components or features, e.g. polysaccharideamendments or a fungal inoculum, to provide even further improved fungalgrowth characteristics. Physically, the AMC is a generally stable,air-rich colloid, which in embodiments may be a foam.

Culturing of a filamentous fungus on or in an AMC may be employed in anyof a wide variety of applications. As a first non-limiting example, useof an AMC may be included in a fermentation strategy for inoculation ina surface fermentation system or process. As a second non-limitingexample, use of an AMC may be included in a fermentation strategy forinoculation in a solid substrate fermentation system or process. As athird non-limiting example, AMCs may be used in “membrane” fermentationsystems, e.g. as disclosed and described in PCT Application Publication2019/046480, or processes without a membrane; in these embodiments, theAMC itself may take the place of a membrane. As a fourth non-limitingexample, AMCs may be used in fermentation “trays” or other similarvessels for the formation of biomats on a surface of the AMC and/or onan air/medium interface therein.

It is to be expressly understood that fungal biomass produced accordingto the methods and systems of the present invention may have anysuitable geometry, and that a fermentation container, surface, or vesselmay be selected to provide the AMC and/or the fungal biomass with thedesired geometry. By way of non-limiting example, where fermentation iscarried out on or within a container or surface, a biomat of thefilamentous fungus may be produced. By way of further non-limitingexample, the AMC may be sprayed, dip-coated, “painted,” or otherwisecoated on a surface of, a substrate or scaffold (e.g. a hydrophobicscreen), whereby the fungal biomass may thus grow in a shape or patternsimilar to a shape or pattern similar to that of the substrate orscaffold, and the shape of the substrate or scaffold may be preselected(e.g. cubical, spherical, etc.) to provide a corresponding desiredfungal geometry.

The methods and systems of the present invention provide for more rapidand prolific growth of filamentous fungus than can be achieved byconventional methods and systems for culturing filamentous fungi.Without wishing to be bound by any particular theory, it is believedthat, in embodiments, this benefit of the methods and systems of thepresent invention may be achieved as a result of the interaction of theAMC with hydrophobins produced by the filamentous fungus. Hydrophobinsare small, cysteine-rich proteins that are naturally expressed by manyspecies of filamentous fungi and self-assemble into a hydrophobicbilayer on hydrophilic/hydrophobic interfaces, such as a water/airinterface. The fungus can then penetrate the hydrophilic/hydrophobicinterface. In conventional surface fermentation, for instance,hydrophobins may form a bilayer on the interface between a liquidfeedstock and the surrounding atmosphere, which is then penetrated byfungal tissues (which lie primarily on the air side of the interface) toreach the liquid feedstock. It is believed that, in the practice of thepresent invention, the AMC, which contains a significant volume fractionof air, greatly increases the effective surface area of the air/mediuminterface and thus the area over which hydrophobins may self-assembleand enable penetration of the fungus to reach the growth medium. Putanother way, an AMC has a much greater effective surface area over whichsurface fermentation can take place than a conventional feedstock in aconventional surface fermentation process.

Methods and systems of the present invention are particularly suitablefor the production of filamentous fungi as a source of food.Specifically, use of an AMC may enable the cultured filamentous fungusto grow much more rapidly and prolifically, without the need for growthenhancers or other additives that may negatively affect the safety,nutritional profile, or taste of the resulting fungus. At the same time,the AMC and/or the filamentous fungus may comprise food-grade orfood-safe additives and ingredients; by way of non-limiting example, theAMC may comprise a food-grade or food-safe foam stabilizer, e.g. xanthangum, which is not harmful if eaten and so does not pose a risk toconsumers if absorbed by the fungus during fermentation. The nutritionalprofile, taste, or other characteristics of the filamentous fungus mayalso be enhanced or augmented by the inclusion of any one or morevarious food-grade or food-safe additives, such as (by way ofnon-limiting example) enrichment of the AMC with certain vitamins,minerals, or other nutrients.

As may be appreciated, various parameters of the AMC may be controlledor tuned to provide for a desired growth profile of the filamentousfungus. As a first non-limiting example, the relative quantity,distribution, bubble size, etc. of air dispersed within a volume of thefermentation medium may be selected to provide a desired foam structure,which may impact the growth of the filamentous fungus as describedherein. As a second non-limiting example, a composition and amount of anoptional foam stabilizer provided as part of the AMC may be selected toprovide a desired foam stability profile over time. As a thirdnon-limiting example, a composition and amount of an optional surfactantprovided as part of the AMC may be selected to provide a desired surfacetension or interfacial tension between any two of the air within theAMC, the liquid fermentation medium within the AMC, and the filamentousfungus; the use of a surfactant may also help to drive, define, and/oraugment various other characteristics of the AMC, the filamentousfungus, and/or the fermentation process, including but not limited to abehavior of an inoculum of the filamentous fungus on or in air bubblesof the AMC, the energy associated with nucleating particles in the AMC,and/or a resultant foam size or volume. In general, then, any attributeor chemical or physical property of the AMC, and of colloids moregenerally, that can affect the surface behavior of the AMC and/or afilamentous fungus disposed therein or thereon may be controlled ortuned to provide for a desired growth profile of the filamentous fungus.

One chemical and/or physical characteristic of the AMC of interest inthe methods and systems of the present invention is a surface activityof a foam stabilizer or surfactant present in the AMC. Specifically, afoam stabilizer or surfactant, if present, may be selected and providedin suitable quantities, based on a surface activity of the foamstabilizer or surfactant in the fermentation medium, to provide adesired surface tension of the AMC. Non-limiting examples of foamstabilizers and surfactants suitable for use in the invention includepolysaccharide gums (e.g. xanthan gum, guar gum, locust bean gum, konjacroot gum), anionic surfactants (e.g. carboxylates, phosphate esters,sulfate esters, sulfonate esters), cationic surfactants (e.g. primary,secondary, or tertiary amines, quaternary ammonium salts), ceteareth 20,cellulose, diacetyl tartaric esters of mono- and diglycerides (DATEM),diglycerides, emulsifying wax, glycerol monostearate, lecithins,monoglycerides, mustards, non-ionic surfactants (e.g. polysorbate 20,polysorbate 80), soaps, sodium phosphates, sodium stearoyl lactylate,zwitterionic surfactants, saponins, starches, modified starches, plantprotein surfactants (e.g. soy protein isolate, pea protein isolate),animal protein surfactants (e.g. casein, whey protein isolate),microparticulates, silica, and combinations and mixtures thereof.

In the practice of the present invention, stabilizers and surfactantsare generally present in an AMC in an amount of between about 0.1 wt %and about 2.5 wt %, or alternatively in any range from about any tenthof a percent by weight to about any other tenth of a percent by weightbetween 0.1 wt % and 2.5 wt %. By way of non-limiting example,stabilizers and surfactants may be present in an AMC in an amount of atleast about 0.1 wt %, at least about 0.2 wt %, at least about 0.3 wt %,at least about 0.4 wt %, at least about 0.5 wt %, at least about 0.6 wt%, at least about 0.7 wt %, at least about 0.8 wt %, at least about 0.9wt %, at least about 1.0 wt %, at least about 1.1 wt %, at least about1.2 wt %, at least about 1.3 wt %, at least about 1.4 wt %, at leastabout 1.5 wt %, at least about 1.6 wt %, at least about 1.7 wt %, atleast about 1.8 wt %, at least about 1.9 wt %, at least about 2.0 wt %,at least about 2.1 wt %, at least about 2.2 wt %, at least about 2.3 wt%, or least about 2.4 wt %. By way of further non-limiting example,stabilizers and surfactants may be present in an AMC in an amount of nomore than about 2.5 wt %, no more than about 2.4 wt %, no more thanabout 2.3 wt %, no more than about 2.2 wt %, no more than about 2.1 wt%, no more than about 2.0 wt %, no more than about 1.9 wt %, no morethan about 1.8 wt %, no more than about 1.7 wt %, no more than about 1.6wt %, no more than about 1.5 wt %, no more than about 1.4 wt %, no morethan about 1.3 wt %, no more than about 1.2 wt %, no more than about 1.1wt %, no more than about 1.0 wt %, no more than about 0.9 wt %, no morethan about 0.8 wt %, no more than about 0.7 wt %, no more than about 0.6wt %, no more than about 0.5 wt %, no more than about 0.4 wt %, no morethan about 0.3 wt %, or no more than about 0.2 wt %.

Another chemical and/or physical characteristic of the AMC of interestin the methods and systems of the present invention is a stability ofthe AMC when the AMC is provided as a foam. Although various assays areknown and described in the literature for assessing the stability of afoam, the simplest methods for determining foam stability include simplymeasuring the height of an upper surface of the foam in the same vesselat two (or more) points in time. The stability of a foam may enable thefoam to be stored and/or transported for a significant period afterformulation, providing yet another advantageous benefit to the methodsand systems of the present invention. In some embodiments when the AMCis a foam, it has a stability of at least about 50%, 60%, 70%, 80%, 90%,or 95% over 1 hour, 6 hours, 12 hours, 1 day, 2 days, 3 days, 4 days, 5days, 6 days, 1 week or 2 weeks.

Still another chemical and/or physical characteristic of the AMC ofinterest in the methods and systems of the present invention is atexture of the AMC when the AMC is provided as a foam. Specifically, anyone or more of the volume, cell structure, overrun, gas fraction,packing geometry, interfacial geometry, and other similar features ofthe foam may be selected and/or designed to provide a desired effect onthe growth of the filamentous fungus, as may be various properties ofthe dispersion medium, such as water activity, ionic strength, osmoticpressure, and the like. In particular, these and other features offoamed AMCs may affect the effective surface area of the AMC availablefor fermentation, which as described throughout this disclosure has asignificant impact on the resulting yield of filamentous fungus.

Yet another chemical and/or physical characteristic of the AMC ofinterest in the methods and systems of the present invention is arelationship between the viscosity and the stability of the AMC when theAMC is provided as a foam. In many applications, such as when processoperations require the AMC to be poured, pumped, stored, and/ortransported, it may generally be desirable to increase the stability ofthe foamed AMC without increasing the AMC's viscosity. The selection ofa desired stability and a desired viscosity may, in turn, affect theselection and/or amount of a provided foam stabilizer, surfactant,thickener, etc.

Yet another chemical and/or physical characteristic of the AMC ofinterest in the methods and systems of the present invention is a molarcarbon-to-nitrogen ratio in the fermentation medium. By way ofnon-limiting example, a molar carbon-to-nitrogen ratio in thefermentation medium may be at least about 10, at least about 11, atleast about 12, at least about 13, at least about 14, at least about 15,at least about 16, at least about 17, at least about 18, at least about19, at least about 20, at least about 21, at least about 22, at leastabout 23, at least about 24, or at least about 25, or between about 10and about 25, or in a range between about any whole number and about anyother whole number between 10 and 25. In some embodiments, a molarcarbon-to-nitrogen ratio in the fermentation medium may preferably bebetween about 12 and about 20.

The AMCs of the present invention may be aerated, or otherwise have airor any other gas dispersed therein, by any suitable means, at aerationrates and for times selected to provide a desired air fraction and/orfoam stability to the AMC. By way of first non-limiting example, wherethe volume of fermentation medium used to form the AMC is relativelysmall, an immersion blender or similar device may be used; typicalhousehold immersion blenders generally comprise two or more blades whichrotate at high speeds (at least about 12,000 rpm) and are thereforewell-adapted to aerate a liquid fermentation medium. By way of secondnon-limiting example, an AMC in the form of a foam may be generated byaerating a liquid growth medium with a static mixing head, and/or bywhipping the liquid growth medium using a whisk, stand mixer, or thelike. By way of third non-limiting example, where the volume offermentation medium used to form the AMC is larger or where moreprecision over the aeration is desired, industrial aeration equipment,such as a high-volume and/or high-shear mixer, with or without an airbubbler, or the application of an applied positive or negative pressure,may be used. Other devices, methods, and systems for forming the AMC,such as the use of static and dynamic mixing heads, bubbling, ascrape-side heat exchanger, extrusion, pressure differential methods,and so on are expressly contemplated and are within the scope of thepresent invention. Control over the aeration may be desirable forvarious reasons, including but not limited to providing the AMC with adesired air cell size; without wishing to be bound by any particulartheory, it is believed that there is a positive correlation between aircell size and viscosity (i.e. smaller air cells result in lowerviscosity, larger air cells result in higher viscosity) and a negativecorrelation between air cell size and foam stability (i.e. smaller aircells result in higher foam stability, larger air cells result in lowerfoam stability).

In the practice of the present invention, inoculation and culturing ofthe filamentous fungus on or in the AMC may take place in any suitablefermentation vessel. Generally, a height, cross-sectional area, and/orvolume of the fermentation vessel may be selected to provide a desiredeffect on the AMC and/or the fermentation process. By way ofnon-limiting example, and without wishing to be bound by any particulartheory, it may be that, ceteris paribus, a greater volume of AMC resultsin greater foam stability (or, equivalently, a slower rate of loss ofvolume or “drainage” of the foam); this may be the result of capillaryaction working against gravity to maintain the keep the AMC in a foamedstate. Foam stability may also be dependent on a drainage ordisproportionation rate of the foam, which may be driven by stability ofthe interfacial surfaces of the colloid and a Laplace pressuredifferential (bubble size and size distribution).

In embodiments in which the AMC is provided in the form of a foam, theinternal physical structure of the foam, i.e. the arrangement of aircells and the network of liquid films separating the air cells may bethought of as a “scaffold” on which biomass or portions of biomass mayadhere and grow. Thus, the structure of this “scaffold” may, in someembodiments, be a particularly important consideration, and the size ofthe air cells or bubbles within the foam, together with other foamparameters, may be selected to provide a desired scaffold structure.Characteristics of the aeration process used to form the AMC from thefermentation medium may be tuned with these or other foamcharacteristics in mind, particularly to provide a desired growthpattern, profile, or rate, e.g. a preselected doubling rate of an areaor mass of the fungal biomass produced by the culturing methods of thepresent invention.

Electrostatic and/or ionic forces on a surface or within a volume of theAMC may also provide a significant effect on the suitability of the AMCfor a desired application or the growth of the cultured filamentousfungus. As a first non-limiting example, certain properties of a foamedAMC, including but not limited to a thickness of the foam, may depend,at least in part, on a pH of the AMC and/or foam stabilizers orthickeners contained therein. As a second non-limiting example, anelectrostatic disjoining pressure of the film may impact a balancebetween forces on the surface of the foam and the capillary forcesdrawing the liquid fermentation medium upward, and thus the formationand composition of certain types of film on the surface of the foam. Asa third non-limiting example, electrochemical interactions at theair/foam interface may promote or inhibit fungal growth or adhesion. Asa fourth non-limiting example, the isoelectric point of a foamstabilizer or surfactant used in the AMC may have additional chemicaland/or physical effects on the AMC and/or the filamentous fungus.

Applications for AMCs

It is to be expressly understood that AMCs according to the presentinvention may suitably be utilized in conjunction with known methods andsystems for culturing filamentous fungi. By way of non-limiting example,an AMC may be used as the feedstock in a membrane fermentation processand/or in a “bioreactor.” Additionally and/or alternatively, AMCs may beused in any suitable fermentation vessel, including but not limited tofabrics, membranes, mesh screens, plates, trays, vats, and othervessels. In particular, mesh screens having pore diameters of up toabout 0.25 millimeters, up to about 0.5 millimeters, up to about 0.75millimeters, up to about 1 millimeter, up to about 1.25 millimeters, upto about 1.5 millimeters, up to about 1.75 millimeters, up to about 2millimeters, up to about 3 millimeters, up to about 4 millimeters, up toabout 5 millimeters, up to about 6 millimeters, up to about 7millimeters, up to about 8 millimeters, up to about 9 millimeters, or upto about 10 millimeters can suitably have AMCs applied thereto in thepractice of embodiments of the present invention.

One advantage of the AMCs of the present invention is that they may beprovided with a viscosity suitable to allow them to be “painted” orotherwise coated onto a surface of a substrate or scaffold, and so donot need to be provided in a vessel having an internal cavity forholding the AMC. In fact, the present inventors have successfully coatedvertically disposed mesh screens with AMCs and cultured filamentousfungus thereon, thus providing not only a desired shape but also adesired spatial orientation of fungal growth. High-viscosity AMCs of thepresent invention may, in some embodiments, take the form of, e.g., aspray foam that may be applied to a desired incubation surface by auser.

Reactors and vessels used in conjunction with AMCs of the presentinvention may be designed to provide certain predefined physicalparameters for the AMC and thus for the culturing or fermentationprocess. Such physical parameters include but are not limited to thephysical parameters described throughout this disclosure.

One advantageous application for the methods and systems of the presentinvention is for the production of filamentous fungus biomass that maybe used as a foodstuff, as a structural material, or as a textile, byway of non-limiting example. In addition, methods and systems of thepresent invention can be for production of desirable metabolic productsof a filamentous fungus. By way of non-limiting example, methods andsystems of culturing a filamentous fungus on or in an AMC according tothe present invention may be exploited to stimulate production of anyone or more of an organic acid, an antibiotic, an enzyme, a hormone, alipid, a mycotoxin, a vitamin, a pigment, and a recombinant heterologousprotein by the filamentous fungus. Among common filamentous fungusmetabolites that may be particularly desirable to synthesize by thesemethods is gibberellic acid, which has a number of importanthorticultural uses, including but not limited to use a germinationstimulant, a production-boosting hormone in grape-growing, a growthreplicator in cherries, and a supplement to citrus fruit crops thatpromotes the growth of seedless fruit. Metabolites produced byfilamentous fungi cultured according to the present invention mayinclude both growth-associated metabolites and non-growth-associatedmetabolites. In some embodiments, production of a desired metabolite mayoptionally be stimulated by milling a solid substrate and adding themilled solid substrate to the AMC prior to or during fermentation.

Biomats produced by the methods and systems disclosed herein may beuseful in a wide variety of applications. By way of first non-limitingexample, biomats produced according to the present invention may betransformed into foodstuffs by any one or more methods known to thoseskilled in the art, for example as disclosed in PCT ApplicationPublications 2019/046480 and 2020/176758. In general, biomats producedaccording to the present invention may be incorporated into foodstuffsin the form of large particles or filaments (e.g. to make a meat analogfood product), fine particles (e.g. to make a flour), a liquiddispersion of particles (e.g. to make a milk analog food product), orany other suitable form. Foodstuffs made from filamentous fungal biomatsproduced according to the methods and systems disclosed herein, whichare subsequently transformed into the foodstuff by any one or more knownmethods and systems, are therefore within the scope of the presentdisclosure.

By way of second non-limiting example, biomats produced according to thepresent invention may be transformed into structural materials, such asbuilding materials, by any one or more methods known to those skilled inthe art, for example as disclosed in U.S. Pat. Nos. 9,555,395 and9,951,307. In general, biomats produced according to the presentinvention may be incorporated into structural materials by beingcombined with a lignocellulosic material or growth medium, or by anyother suitable means. Structural materials made from filamentous fungalbiomats produced according to the methods and systems disclosed herein,which are subsequently transformed into the structural material by anyone or more known methods and systems, are therefore within the scope ofthe present disclosure.

By way of third non-limiting example, biomats produced according to thepresent invention may be transformed into textiles, such as leatheranalog textiles, by any one or more suitable methods. Most typically,such methods may include causing a solution of a polymer and/orcrosslinker to infiltrate the biomat (which may optionally bepreviously, simultaneously, or subsequently size-reduced) and thencuring the biomat to remove the solvent, but in the most general sense,biomats produced according to the present invention may be transformedinto textiles by any suitable method of modifying chemical or physicalproperties of the biomat (e.g. by crosslinking, combining with a polymeror other structural reinforcing material, etc.) to provide a desiredmaterial or mechanical property. Textiles made from filamentous fungalbiomats produced according to the methods and systems disclosed herein,which are subsequently transformed into the textile by any one or moresuitable methods and systems, are therefore within the scope of thepresent disclosure.

Growth and Microstructure of Fungal Biomass

In the practice of the methods of the present invention, fungal biomassmay be produced that has a desired growth characteristic, which in manycases will correspond to a desired chemical or physical structure, inparticular a physical microstructure, of the fungal biomass. By way offirst non-limiting example, a biomass that has a desired spatialdistribution of AMC constituents throughout the biomass may be producedby the methods disclosed herein. By way of second non-limiting example,a desired spatial distribution of a fungal inoculum throughout the AMCmay be achieved by the methods disclosed herein (which may, in turn,result in production of a biomass having a desired physicalcharacteristic). By way of third non-limiting example, a desired patternof mycelial network nucleation and/or development may be achieved by themethods disclosed herein, particularly by modification or tuning ofparticular AMC and/or inoculum characteristics. By way of fourthnon-limiting example, a biomass having a spatially varying physicalcomposition, e.g. having spatial variations in the concentration ofparticular fungal tissues, may be produced by the methods disclosedherein. By way of fifth non-limiting example, a biomass having aspatially varying chemical composition or behavior, e.g. having spatialvariations in respiration rate, protein content, nutrient (e.g. carbonor nitrogen) utilization, and the like, may be produced by the methodsdisclosed herein. By way of sixth non-limiting example, a biomass havinga desired metabolic characteristic, e.g. a preselected metabolicefficiency, increased or decreased production of a selected metabolite,etc., may be produced by the methods disclosed herein. By way of seventhnon-limiting example, a biomass having a desired carbon dioxideproduction rate or profile may be produced by the methods disclosedherein. By way of eighth non-limiting example, production of a biomassmay be effectively segregated into distinct stages, e.g. initialnucleation, combination of nucleation sites, evolution of a thincohesive film, vertical growth of the biomass, evolution and growth ofdistinct layers of biomass, etc., by the methods disclosed herein (whichmay, in turn, result in production of a biomass having a desiredphysical characteristic). By way of ninth non-limiting example, abiomass having a desired characteristic relevant to a consumer of thefilamentous fungus as a food product, e.g. biomass (dry) density,conversion efficiency, nutrient profile, taste, visual appearance,aroma, protein binding, mycotoxin content, etc., may be produced by themethods disclosed herein; in some embodiments, a dry density of thebiomat may be at least about 0.19 g/cm³, at least about 0.20 g/cm³, atleast about 0.21 g/cm³, or at least about 0.22 g/cm³. By way of tenthnon-limiting example, a biomass having a desired wet density may beproduced by the methods disclosed herein, which may improve thesuitability of the biomass for use in a desired application (e.g. asfood, as a textile material, etc.) and/or improve the ease with whichthe biomass may be subsequently processed.

In some embodiments, particularly those in which the AMC is provided inthe form of a foam, cells of the filamentous fungus may remainpreferentially sequestered in the foam after harvesting of the biomats,with filaments of fungus adhered to the surface of bubbles within thefoamed AMC. This may be advantageous or desirable in applications inwhich, for example, the AMC may be subsequently processed to obtainfurther biomass from the surface of bubbles within the AMC.

In some embodiments, growth of a filamentous fungal biomat on an AMC mayresult in a biomat having a decreased or minimized content ofmicroconidia and/or an increased or maximized content of fungal hyphae.By way of non-limiting example, microconidia may make up less than about50%, less than about 40%, less than about 30%, less than about 20%, lessthan about 10%, less than about 5%, less than about 4%, less than about3%, or less than about 2% of a filamentous fungal biomat producedaccording to the present invention. By way of further non-limitingexample, fungal hyphae may make up at least about 50%, at least about60%, at least about 70%, at least about 80%, at least about 90%, atleast about 95%, at least about 96%, at least about 97%, or at leastabout 98% of a filamentous fungal biomat produced according to thepresent invention. Without wishing to be bound by any particular theory,it is believed that filamentous fungal biomats having an increased ormaximized content of fungal hyphae may be particularly useful orsuitable for certain application, e.g. in textile materials, due tomaterial or mechanical properties resulting from this increased ormaximized hyphal content, e.g. increased tensile strength.

Rheology and Structure of AMC Foams

The methods and systems of the invention described herein may be used toproduce AMCs having desired physical and mechanical properties, andparticularly to produce AMC foams having desired rheologies and relatedcharacteristics. By way of first non-limiting example, properties of theair cells dispersed throughout the AMC, e.g. void fraction, bubble size,bubble size distribution, bubble shape, and bubble surface area, may becharacterized and controlled according to the present invention. By wayof second non-limiting example, degradation properties of the AMC, e.g.foam stability as a function of time, chemical degradation pathways ofthe foam, and physical interactions with a fungal inoculum as a functionof time, may be characterized and controlled according to the presentinvention, particularly by use of varying AMC chemistries and fungalinoculum species and loading rates. As a third non-limiting example,fluid properties of the AMC, e.g. viscosity, rheology, power law orBingham plastic behavior, may be characterized and controlled accordingto the present invention, particularly by controlling the gas fractionof the AMC. By way of fourth non-limiting example, working properties ofthe AMC, e.g. shear thinning or shear thickening properties, may becharacterized and controlled according to the present invention. By wayof fifth non-limiting example, changes in chemical or physical behaviorof the AMC over time may be characterized and controlled according tothe present invention, particularly by varying a loading rate of thefungal inoculum. By way of sixth non-limiting example, effects of foamstabilizers and surfactants, e.g. hydrophobins and xanthan gum, may becharacterized and controlled according to the present invention. By wayof seventh non-limiting example, effects of other additives, e.g.nutrient supplements, may be characterized and controlled according tothe present invention. By way of eighth non-limiting example, the effectof foam formation mechanism, e.g. static packing, rotor/statorformation, and air induction, may be characterized and controlledaccording to the present invention.

Other Process Considerations, Advantages, and Benefits

In many embodiments, it may be desirable to include a foaming agent,foam stabilizer, surfactant, or the like in AMCs of the presentinvention. As described throughout this disclosure, xanthan gum is avery commonly used foam stabilizer and is safe for use in food-gradeapplications. However, many other gums, foaming agents, foamstabilizers, surfactants, thickeners, and so on are known and describedin the art, and may suitably be used in the practice of the presentinvention. These additives may, in embodiments, have differing effectson the stability and other parameters of the AMC and may be selected forsuitability in a particular application. Examples of foaming agents,foam stabilizers, and/or surfactants that may suitably be used in thepractice of the present invention include but are not limited to anionicsurfactants (e.g. carboxylates, phosphate esters, sulfate esters,sulfonate esters), cationic surfactants (e.g. primary, secondary, ortertiary amines, quaternary ammonium salts), ceteareth 20, cellulose,diacetyl tartaric esters of mono- and diglycerides (DATEM),diglycerides, emulsifying wax, lecithins, monoglycerides, mustards,nonionic surfactants (e.g. amine oxides, ethoxylates, fatty acid estersof polyhydroxy compounds, phosphine oxides, sulfoxides), polysorbate 20,soaps, sodium phosphates, sodium stearoyl lactylate, zwitterionicsurfactants, saponins, starches, modified starches, and protein isolatesfrom both plant and animal sources.

In embodiments, two or more stabilizers, surfactants, thickeners, etc.may be provided, and in some cases may have a synergistic effect on foamstability that is greater than simple additive extrapolation of theirseparate effects would predict. Particularly, when xanthan gum is usedin combination with a galactomannan (e.g. guar gum, locust bean gum)and/or glucomannan (e.g. konjac gum) polymer, the present inventors havefound that stable foams may be produced at xanthan addition rates of aslittle as 0.025 wt % of the fermentation medium. AMCs of theseembodiments may exhibit both shear thinning (e.g. lower viscosity athigher shear rate) and heat thinning (e.g. lower viscosity at highertemperature), which may be desirable in certain applications of thepresent invention.

The chemical composition of the fermentation medium may itself beselected to achieve a desired growth rate, composition, etc. of thefungal biomass. In particular, the identity of the carbon source, e.g.fructose, in the fermentation medium may have a significant impact onsuch outcomes as growth profile, carbon utilization rate, and the like.

The fermentation medium may, in embodiments, be or comprise a feedstockcomprising a carbon source and a nitrogen source, and particularly maybe or comprise a feedstock suitable for use in a bioreactor fermentationprocess. Suitable carbon sources are sugars (e.g. sucrose, maltose,glucose, fructose, Japan rare sugars, etc.), sugar alcohols (e.g.glycerol, polyol, etc.), starch (e.g. corn starch, etc.), starchderivative (e.g. maltodextrin, cyclodextrin, glucose syrup, hydrolysatesand modified starch), starch hydrolysates, hydrogenated starchhydrolysates (HSH; e.g. hydrogenated glucose syrups, maltitol syrups,sorbitol syrups, etc.), lignocellulosic pulp or feedstock (e.g. sugarbeet pulp, agricultural pulp, lumber pulp, distiller dry grains, brewerywaste, etc.), corn steep liquors, acid whey, sweet whey, milk serum,wheat steep liquors, carbohydrates, food waste, olive oil processingwaste, hydrolysate from lignocellulosic materials, corn wet millingproduces (e.g. carbon refined syrups, demineralized syrups, enzymeconverted syrups, etc.) and/or combinations thereof. The feedstock canbe a waste product, such as naturally occurring urine and/or feces, foodwaste, plant material, industrial waste such as glycerol, and wasteby-products, starch and/or by products of starch hydrolysis, acid whey,sugar alcohol, and/or combinations thereof. Synthesized or manufacturedwaste surrogates, such as surrogate human urine can also be used. Plantmaterial feedstocks are typically lignocellulosic. Some examples oflignocellulosic feedstock are agricultural crop residues (e.g. wheatstraw, barley straw, rice straw, small grain straw, corn stover, cornfibers (e.g. corn fiber gum (CFG), distillers dried grains (DDG), corngluten mean (CGM), switch grass, sugar beet pulp, waste streams frompalm oil production, hay-alfalfa, sugarcane bagasse, non-agriculturalbiomass (e.g. algal biomass, cyanobacterial biomass, urban treeresidue), forest products and industry residues (e.g., softwoodfirst/secondary mill residue, hard softwood first/secondary millresidue, recycled paper pulp sludge), lignocellulosic containing waste(e.g. newsprint, waste paper, brewing grains, used rubber tire (URT),municipal organic waste and by-products, yard waste and by-products,clinical organic waste and by-products, and waste and by-productsgenerated during the production of biofuels (e.g. processed algalbiomass, glycerol), and combinations thereof.

The AMC may, optionally, further comprise one or more salts. In manyfungal culturing and fermentation processes, salts such as ammoniumnitrate are often used to boost the metabolic activity and/or growthrate of the fungus. These and other salts may be used for similarpurposes in the AMCs of the present invention.

The AMC may, optionally, further comprise one or more other food-gradeadditives. These additives may be provided for any of several purposes,from modifying the physical behavior of the colloid to modifying a tasteor nutritional content of the resulting biomass.

Generally, any filamentous fungus suitable for culture and fermentationin the methods and systems of the prior art may likewise be used in thepractice of the present invention. Such fungi include, but are notlimited to, Fusarium venenatum, Morel mushrooms, pearl mushrooms, andother mushrooms suitable for consumption as food by humans. Moregenerally, the filamentous fungus may belong to an order selected fromthe group consisting of Ustilaginales, Russulales, Polyporales,Agaricales, Pezizales, and Hypocreales; may belong to a family selectedfrom the group consisting of Ustilaginaceae, Hericiaceae, Polyporaceae,Grifolaceae, Lyophyllaceae, Strophariaceae, Lycoperdaceae, Agaricaceae,Pleurotaceae, Physalacriaceae, Omphalotaceae, Tuberaceae, Morchellaceae,Sparassidaceae, Nectriaceae, and Cordycipitaceae; and/or may belong to aspecies selected from the group consisting of Ustilago esculenta,Hericulum erinaceus, Polyporous squamosus, Grifola fondosa, Hypsizygusmarmoreus, Hypsizygus ulmarius, Calocybe gambosa, Pholiota nameko,Calvatia gigantea, Agaricus bisporus, Stropharia rugosoannulata,Hypholoma lateritium, Pleurotus eryngii, Pleurotus ostreatus, Tuberborchii, Morchella esculenta, Morchella conica, Morchella importuna,Sparassis crispa, Fusarium venenatum, MK7 ATCC Accession Deposit No.PTA-10698, Disciotis venosa, and Cordyceps militaris. It is to bespecifically appreciated that an inoculum of a fungus may behaveidentically when cultured in or on an AMC relative to a conventionalgrowth medium, or the inoculum may have additional or alternativeadvantageous or beneficial behavior characteristics when cultured in oron an AMC relative to a conventional growth medium; thesecharacteristics include, but are not necessarily limited to, aggregationbehavior, growth pattern or rate, and so on. The spatial distribution ofthe inoculum on the growth surface may likewise be selected to provide adesired effect on fungal growth pattern, AMC foam morphology orstructure, and so on.

In embodiments, the AMC may be provided as a layer or coating on anothergrowth surface. Such additional and/or alternative growth surfacesinclude, but are not necessarily limited to, a solid surface, asynthetic mesh, a lignocellulosic material such as cotton, and the like.

As described throughout this disclosure, electrochemical properties ofthe AMC may be modified, selected, and/or tuned to improve or control agrowth profile of the filamentous fungus. Examples of electrochemicalproperties of the AMC that may be modified, selected, and/or tunedaccording to the present invention include electrical conductivity andzeta potential.

In the practice of the present invention, AMCs, once produced, may ormay not be actively aerated during fermentation of the filamentousfungus. Decisions as to whether and under what conditions to activelyaerate the AMC during fermentation can, in embodiments, be driven byequipment and resource availability and desired characteristics of thebiomass to be produced, among other considerations. Likewise, foamstabilizers (e.g. xanthan gum), surfactants, and other additives may ormay not be used in AMCs of the present invention, depending on these andother considerations.

An important consideration in the practice of the present invention isthe manner and rate of air transfer to, across and/or through thefermentation surface. Specifically, by culturing filamentous fungus inor on an AMC, the present invention increases the effective surface areaavailable for active fermentation. Fermentation may thus be carried out,for example, on the surface of air bubbles, cells, or pockets within theAMC; stated slightly differently, where previous fermentation processeshave generally limited the fermentation to a “2D” or planar region (i.e.the air/medium interface or surface), the present invention allows for“3D” fermentation of a much greater portion of the spatial extent orvolume of the fermentation medium. Effectively, then, the presentinvention improves upon natural fungal growth processes, without theneed for shear or active aeration, particularly when accounting for airdiffusion through air bubbles, cells, or pockets dispersed throughoutthe AMC. The resulting 3D structure and porosity of the fungal networkmay, in embodiments, allow for an increased or tuned gas diffusion rateor gas permeation rate through the fungal network.

The methods and systems of the present invention have various advantagesand benefits relative to previous methods and systems for the productionof filamentous fungus biomass. A first non-limiting advantage and/orbenefit of the present invention is that active aeration or agitation ofthe liquid fermentation medium is not needed subsequent to the initialformation of the AMC; in particular, where other fermentation processesare generally aerobic processes that rely primarily on passive (ratherthan active) oxygen transfer, the present invention increases anair-to-medium ratio in a more stable and controllable manner and thuspermits precise regulation of air exchange. A second non-limitingadvantage and/or benefit of the present invention is in situ aggregationof fungal biomass into a single coherent mat, such that the mat hassignificant tensile strength to allow for easy harvesting. A thirdnon-limiting advantage and/or benefit of the present invention is thatthe methods and systems of the invention are effective to producetextured biomass, which can be used in a wide variety of products, e.g.food, bioplastics, biofuels, nutritional supplements, and expressionplatforms for a variety of pharmaceuticals. A fourth non-limitingadvantage and/or benefit of the present invention is a significantreduction in water consumption and other residual waste products perkilogram of biomass produced, particularly regarding waste of thefermentation medium itself. A fifth non-limiting advantage and/orbenefit of the present invention is more rapid biomass production; acohesive biomat can, according to the present invention, be produced inas little as eighteen hours. A sixth non-limiting advantage and/orbenefit of the present invention is increased biomass density in abiomat. A seventh non-limiting advantage and/or benefit of the presentinvention is that the methods and systems of the invention may beemployed to produce biomass of any of a wide variety of filamentousfungi, including extremophiles, allowing selection of a filamentousfungus having specific advantages for a desired application. An eighthnon-limiting advantage and/or benefit of the present invention isimproved scalability, allowing for production capacities and rates to bestraightforwardly adjusted or modified without affecting theproductivity of the methods and systems of the invention. A ninthnon-limiting advantage and/or benefit of the present invention is theability to utilize a wide variety of carbon- and/or nitrogen-richsubstrates, including those produced during space missions or naturaldisasters, as a productive fermentation medium for the culture andproduction of filamentous fungi.

In some embodiments, methods of the present invention may produce an“area yield,” defined herein as a mass of biomat per top surface area ofthe AMC on which the biomat is grown, of at least about 0.5 kg/m², atleast about 0.6 kg/m², at least about 0.7 kg/m², at least about 0.8kg/m², at least about 0.9 kg/m², at least about 1.0 kg/m², at leastabout 1.1 kg/m², at least about 1.2 kg/m², at least about 1.3 kg/m², atleast about 1.4 kg/m², at least about 1.5 kg/m², at least about 1.6kg/m², at least about 1.7 kg/m², at least about 1.8 kg/m², at leastabout 1.9 kg/m², or at least about 2.0 kg/m². In particular embodiments,such yields may be achieved when stabilizers are used in amounts of atleast about 0.1 wt %, at least about 0.2 wt %, at least about 0.3 wt %,at least about 0.4 wt %, at least about 0.5 wt %, or at least about 0.6wt %, and particularly when the stabilizer comprises xanthan gum. Inparticular embodiments, such yields may be achieved when a molarcarbon-to-nitrogen ratio in the fermentation medium is between about 10and about 23, or between about 11 and about 22, or between about 12 and21, or between about 13 and about 20, or between about 14 and about 19,or between about 15 and about 18, or between about 16 and about 17. Inparticular embodiments, such yields may be achieved when a viscosity ofthe AMC is no more than about 12,000 cP, or no more than about 11,000cP, or no more than about 10,000 cP, or no more than about 9,000 cP, orno more than about 8,000 cP, or no more than about 7,000 cP.

In some embodiments, methods of the present invention may produce abiomat having a dry mass density of at least about 0.15 g/cm³, at leastabout 0.16 g/cm³, at least about 0.17 g/cm³, at least about 0.18 g/cm³,at least about 0.19 g/cm³, at least about 0.20 g/cm³, at least about0.21 g/cm³, or at least about 0.22 g/cm³. In particular embodiments,such densities may be achieved when stabilizers are used in amounts ofat least about 0.1 wt %, at least about 0.2 wt %, at least about 0.3 wt%, at least about 0.4 wt %, at least about 0.5 wt %, or at least about0.6 wt %, and particularly when the stabilizer comprises xanthan gum. Inparticular embodiments, such densities may be achieved when a molarcarbon-to-nitrogen ratio in the fermentation medium is between about 10and about 23, or between about 11 and about 22, or between about 12 and21, or between about 13 and about 20, or between about 14 and about 19,or between about 15 and about 18, or between about 16 and about 17. Inparticular embodiments, such densities may be achieved when a viscosityof the AMC is no more than about 12,000 cP, or no more than about 11,000cP, or no more than about 10,000 cP, or no more than about 9,000 cP, orno more than about 8,000 cP, or no more than about 7,000 cP.

In some embodiments, methods of the present invention may produce abiomat having a tensile strength, either before or after being boiled,of at least about 255 kPa, at least about 260 kPa, at least about 265kPa, at least about 270 kPa, at least about 275 kPa, at least about 280kPa, at least about 285 kPa, at least about 290 kPa, at least about 295kPa, or at least about 300 kPa. In particular embodiments, such tensilestrengths may be achieved when stabilizers are used in amounts of atleast about 0.1 wt %, at least about 0.2 wt %, at least about 0.3 wt %,at least about 0.4 wt %, at least about 0.5 wt %, or at least about 0.6wt %, and particularly when the stabilizer comprises xanthan gum. Inparticular embodiments, such tensile strengths may be achieved when amolar carbon-to-nitrogen ratio in the fermentation medium is betweenabout 10 and about 23, or between about 11 and about 22, or betweenabout 12 and 21, or between about 13 and about 20, or between about 14and about 19, or between about 15 and about 18, or between about 16 andabout 17. In particular embodiments, such tensile strengths may beachieved when a viscosity of the AMC is no more than about 12,000 cP, orno more than about 11,000 cP, or no more than about 10,000 cP, or nomore than about 9,000 cP, or no more than about 8,000 cP, or no morethan about 7,000 cP.

In some embodiments, methods of the present invention may produce abiomat having a thickness of at least about 1.75 mm, at least about 1.80mm, at least about 1.85 mm, at least about 1.90 mm, at least about 1.95mm, at least about 2.00 mm, at least about 2.05 mm, at least about 2.10mm, at least about 2.15 mm, at least about 2.20 mm, at least about 2.25mm, or at least about 2.30 mm. In particular embodiments, suchthicknesses may be achieved when stabilizers are used in amounts of atleast about 0.1 wt %, at least about 0.2 wt %, at least about 0.3 wt %,at least about 0.4 wt %, at least about 0.5 wt %, or at least about 0.6wt %, and particularly when the stabilizer comprises xanthan gum. Inparticular embodiments, such thicknesses may be achieved when a molarcarbon-to-nitrogen ratio in the fermentation medium is between about 10and about 23, or between about 11 and about 22, or between about 12 and21, or between about 13 and about 20, or between about 14 and about 19,or between about 15 and about 18, or between about 16 and about 17. Inparticular embodiments, such thicknesses may be achieved when aviscosity of the AMC is no more than about 12,000 cP, or no more thanabout 11,000 cP, or no more than about 10,000 cP, or no more than about9,000 cP, or no more than about 8,000 cP, or no more than about 7,000cP.

It is to be expressly understood that although the present invention hasgenerally been described as utilizing colloids of air in a liquidfermentation medium, any gas suitable for use in a fungal culture orgrowth process may be dispersed in a foam in addition to or instead ofair. Indeed, the gas to be dispersed in the foam may, in embodiments, beselected to achieve, by way of non-limiting example, a chemical orphysical composition of the resulting fungal biomass that cannot beachieved using air.

The invention is further described with reference to the followingillustrative, non-limiting Examples.

Example 1

This Example illustrates the use of a foam stabilizer in an AMC of thepresent invention and demonstrates that significantly improved yields ofbiomass and reduced tray waste can be achieved by use of a foamstabilizer.

Six AMCs were prepared by aerating a volume of standard inoculated MK102fermentation medium, the composition of which (on a basis of nine litersof total medium) is defined in Table 1, with a typical householdimmersion blender (12000 rpm) for 15 seconds and pouring 200 mL of theaerated fermentation medium into a glass tray having a surface area of0.02 m². Four of the six prepared AMCs contained up to 0.4 wt %food-grade xanthan gum as a stabilizer.

TABLE 1 Ingredient Amount Ammonium nitrate 91.329 g Urea 30.805 gCalcium chloride dihydrate 11.922 g Magnesium sulfate heptahydrate 9.000g Monopotassium phosphate 36.000 g Trace EDTA 3.600 mL Glycerol 0.900 kgYeast extract 13.500 g Water 8.286 L Concentrated hydrogen chloride 7.3mL (to adjust pH to 2.7)

All AMCs were observed to be pourable, self-leveling, and sufficientlyinviscid to be pumped using standard equipment. AMCs comprising 0.1 wt %xanthan gum or less did not form stable foams, while AMCs comprisingmore than 0.1 wt % xanthan gum formed substantially homogeneous foamsthat remained stable for the duration of the experiment. It was alsoobserved that the AMCs containing xanthan gum exhibited both continuousphase gelation and shear thinning, behaving as fluids when stirred orpumped but as a gel when at rest.

An inoculum of MK7 ATCC Accession Deposit No. PTA-10698 was introducedonto the surface of each AMC, and the six trays containing the AMCs wereplaced in an incubator and cultured for four days. After the four-dayculture period, biomats of the filamentous fungus were harvested andprocessed by steaming (to inactivate the fungus) and pressing (to removewater). Various parameters of the mats were measured; the results aregiven in Table 2.

TABLE 2 Sample Xanthan Pre-processing Post-processing Yield # wt % mass(g) mass (g) Solids % (kg/m²) 1 0 25.096 10.503 24 0.52 2 0 21.31510.416 23 0.52 3 0.1 31.721 10.391 24 0.52 4 0.2 64.233 38.480 18 1.9 50.3 51.993 34.011 25 1.7 6 0.4 51.500 28.100 26 1.4

All biomats had acceptable coloration, odor, and tensile strength.

FIG. 1 is an image of the biomats obtained (from left to right, top tobottom: Sample #6, Sample #3, Sample #1, Sample #2, Sample #5, Sample#4). As illustrated in Table 1 and FIG. 1, AMCs in the form of stablefoams produced significantly enhanced yields of biomat relative tounstable foams.

FIG. 2 is an image of the trays in which a control sample (top), Sample#4 (bottom left), and Sample #5 (bottom right) were cultured. Asillustrated in FIG. 2, the proportion of fermentation medium remainingin the tray after fermentation, i.e. “tray waste,” is greatly reducedfor samples grown on stable foam AMCs. This is consistent with thehypothesis that stable AMCs provide a greater effective surface area forfermentation and therefore readier availability of the fermentationmedium to the filamentous fungus. Without wishing to be bound by anyparticular theory, it is believed that this greater effective surfacearea reduces tray waste by allowing the filamentous fungus to convert agreater proportion of the nutrients in the growth medium into biomass,increasing the biomat. Photomicrographs (not illustrated) of the AMCsappeared to indicate that fungal cells remained preferentiallysequestered in the foam after harvesting of the biomats, with filamentsof fungus adhered to the surface of bubbles within the foamed AMCs.

Example 2

This Example illustrates a comparison between growth of a filamentousfungus on an AMC and growth of a filamentous fungus in a conventionalsurface fermentation process and demonstrates that significantlyaccelerated growth, and significantly improved yields, of biomass can beachieved by use of an AMC.

An inoculum of MK7 ATCC Accession Deposit No. PTA-10698 was introducedonto the surface of each of six fermentation media in growth chambers:three conventional liquid media, and three AMCs according to the presentinvention. For each of the six media, the total volume of fermentationmedium in the growth chamber was 1750 mL and the top surface area was0.25 m². The fungi were then allowed to incubate on each medium for aperiod of 96 hours; starting at 36 hours after inoculation, total fungalgrowth was measured at intervals of six to eight hours. The results arepresented in Table 3 and FIG. 3 (in FIG. 3, the mean growth from thethree surface fermentations and the three AMC fermentations is given).

TABLE 3 Time Surface fermentation area yield (g/m², dry) AMCfermentation area yield (g/m², dry) (hours) Tray 1 Tray 2 Tray Mean Tray1 Tray 2 Tray 3 Mean 36 11.6 15.2 15.2 13.92 36.0 28.4 24.8 29.68 4430.0 40.8 44.8 38.64 80.8 66.8 67.6 71.72 52 68.4 90.8 86.0 81.72 122.8117.2 156.8 132.28 60 113.6 117.2 113.2 114.68 173.2 172.8 178.4 174.7268 194.8 194.4 174.0 187.8 250.8 255.2 219.6 241.84 76 124.0 295.6 240.0219.92 288.8 306.8 286.4 294.04 84 174.0 294.8 305.6 258.28 300.0 308.8338.4 315.72 90 288.0 340.8 — 314.24 319.2 276.4 — 297.76 96 — — 349.6349.76 — — 382.0 381.84

Example 3

This Example illustrates a comparison of fungal structure andcomposition between surface-fermented fungus and AMC-fermented fungusand demonstrates that AMC fungal fermentation processes can be utilizedto provide markedly different fungal structure and composition thanconventional surface fermentation processes.

Extracts of the surface-fermented and AMC-fermented fungi grown inExample 2 were pH-buffered and subsequently assayed for protein content;the extracts were also lysed by bead beating, in some cases before andin some cases after pH adjustment. FIG. 4 shows results of these proteinassays for the surface-fermented fungi, and FIG. 5 shows results ofthese protein assays for the AMC-fermented fungi (labeled “AME” in thefigure).

As FIGS. 4 and 5 illustrate, fungi produced by AMC fermentation haveapproximately double the extractable protein content of fungi producedby conventional surface fermentation. Without wishing to be bound by anyparticular theory, it is believed that this difference in proteincontent is due to a structural difference in the growth pattern of thetwo fermentation processes; specifically, it is believed that AMCfermentation results in a larger content of fungal hyphae, and a muchlower content of microconidia, than conventional surface fermentation.The present inventors estimate that the fungus produced by AMCfermentation is approximately 1% microconidia, whereas the fungusproduced by conventional surface fermentation is approximately 50%microconidia.

Another possible explanation for the difference in protein contentbetween AMC-grown mats and mats grown by conventional surfacefermentation, without wishing to be bound by any particular theory, is adifference in the fungal growth environment. In AMC fermentation, alarge percentage of fungal growth occurs at the air/medium interface,e.g. on the surface of bubbles of air within the AMC; mycelia growing onsuch surfaces are exposed to differences in, for example, oxygen accessand effective surface tension as compared to fungal tissues growing in asolution or underneath other mycelia. It may thus be possible thatbiomats grown on AMCs exhibit differences in, e.g., protein content dueto an increased “surface effect,” or in other words due to the fact thata greater share of the fungal biomass was grown on a surface rather thanin solution or in an interior of a mycelial mass.

Example 4

This Example illustrates the use of AMCs of the present invention topromote fungal growth on the surface of a mesh substrate. 200 mL of asynergistically gelled AMC was prepared from inoculated MK102 growthmedium by addition of gums (0.4 wt % locust gum, 0.2 wt % whey proteinisolate) and a surfactant (0.4 wt % xanthan gum), followed byintroduction of air via vortex using a KitchenAid immersion blender(10,000 rpm) for 60 seconds. The AMC was then applied to the surface ofa 2 mm×2 mm hydrophobic polyolefin mesh that was supported by ascaffold; due to the high viscosity of the AMC, it was possible tospread the AMC on the surface of the mesh with no drainage or dripping.The mesh was then placed in an incubator at 27° C. for 72 hours,whereupon the fungal biomass was harvested from both top and bottomsurfaces of the mesh. FIGS. 6A and 6B are top and bottom views,respectively, of the mesh substrate before harvesting, and FIG. 7illustrates the mesh substrate after harvesting.

This test yielded a total fungal biomass of 26.556 g, with approximatelyequal masses of fungal biomass harvested from both the top and bottomsurfaces of the mesh substrate. As FIGS. 6A and 6B illustrate, both matswere substantively identical, although the lower mat had a slightlygreater moisture content (presumably due to gravity). After 45 minutesof steaming, the processed biomass had a visual appearance and an odorthat were not apparently different from those of fungal biomass producedby conventional surface fermentation. This Example thus illustratesthat, unlike conventional fermentation media that require a traditionalcontainer (dish, plate, tray, etc.), AMCs of the present invention canbe used to culture filamentous fungi on surfaces, including poroussurfaces, without flowing or drainage of the AMC.

Example 5

This Example illustrates the effects on fungal growth of varioussurfactants, thickeners or stabilizers, carbon sources, and growthmedium salts.

MK102 growth medium was poured into each of several 5×7 glass trays andaerated to produce an AMC. Various additional gum products, emulsifiers,carbon sources, and so on were added to or modified in some samples, asshown in Table 4 below. The carbon source in each medium was present at10 wt %. Each AMC was then inoculated with a fungal inoculum and allowedto incubate for 70 hours. Table 4 shows the yield and pH of the fungusproduced from each AMC, as well as a subjective, binary indication ofwhether the color and smell of the biomass were or were not acceptable(i.e. sufficiently similar to surface fermentation). The volume ofmedium in each tray was 200 mL unless otherwise noted.

TABLE 4 Yield Color Smell Sample (g) pH acceptable? acceptable? MK103NX200 56 2.76 No No MK103 CX90 WPI 18 5.30 No No MK103 CX90 56 2.98 NoNo MK103 NX200 GS 42 2.98 No No MK103 NX200 WPI 68 3.27 No No .5 G .5MNX200 25 6.71 Yes Yes .5 G .5M NX200 LBG .5 V 58 6.27 Yes Yes .5 G .5MNX200 WPI 40 5.97 Yes Yes .5 G .5M NX200 LBG .25 V 35 n/a Yes Yes Y-M+WPI + 1 g fructose 28 4.24 Yes Yes Y-M+ CX90 WPI 30 6.17 Yes Yes Y-M+NX200 WPI 46 6.00 Yes Yes Y-M+ WPI + 0.5 g fructose 46 5.51 Yes YesMK102 + 1 g fructose 48 5.74 No Yes MK102 + 0.5 g fructose 52 6.09 NoYes Legend: NX200, CX90 = xanthan gum (0.4 wt %) LBG = locust bean gum(0.4 wt %) WPI = whey protein isolate (0.2 wt %) GS = glycerol stearate(AKA glycerol monostearate) (0.2 wt %) .5 G .5M = 50% of glycerol inMK102 medium substituted with malt extract Y-M+ = MK102 medium yeastextract replaced with malt extract .25 V = ¼ volume (50 mL) .5 V = ½volume (100 mL)

Example 6

This Example illustrates the effects on fungal growth of varioussurfactants, thickeners or stabilizers, carbon sources, and growthmedium salts.

The procedure of Example 5 was repeated, subject to the followingmodifications. None of the media used in Example 6 included nitratesalts; instead, the ammonium nitrate of typical MK102 growth medium wasreplaced with ammonium chloride at equal molarity. All mediaformulations contained 0.4 wt % NX200 xanthan gum, except for theformulations denoted “control.” All results given in Table 5 are theaverage of two test runs, with the exception of the entries denoted by asuperscript “1” (one test run) or “3” (three test runs, one resulting inno mat growth).

TABLE 5 Carbon Yield Color Smell source Additives (g) pH acceptable?acceptable? 100% None 24.553 2.09 Yes Yes fructose GS 17.947 2.00 YesYes WPI 17.156 2.04 Yes Yes LBG 16.343 1.96 Yes Yes LBG + GS 18.254 2.00Yes Yes Control¹ 9.080 2.16 Yes Yes 50% None 9.745 2.12 Yes Yes maltextract GS¹ 13.266 2.20 Yes Yes 50% WPI 13.390 2.16 Yes Yes glycerol LBG9.595 2.15 Yes Yes LBG + GS 17.295 2.16 Yes Yes Control¹ 0.000 n/a n/an/a 100% None 15.511 2.46 Yes Yes malt extract GS 12.002 2.28 Yes YesLBG¹ 10.922 2.27 Yes Yes LBG + GS¹ 23.862 2.60 Yes Yes WPI 13.158 2.27Yes Yes Control¹ 8.757 2.50 Yes Yes 100% None 9.496 2.27 Yes Yesglycerol GS 9.912 2.21 Yes Yes WPI 12.092 2.20 Yes Yes LBG 11.020 1.99Yes Yes LBG + GS¹ 10.391 2.12 Yes Yes Control¹ 0.000 n/a n/a n/a MK102control³ 32.999 3.30 Yes Yes

Example 7

This Example illustrates the effects on fungal growth of varioussurfactants, thickeners or stabilizers, carbon sources, and growthmedium salts.

The procedure of Example 5 was repeated, subject to the followingmodifications. The total incubation time was modified to 48, 68, or 72hours, as shown in Table 6. The carbon source for the test runs was 100%fructose (M1 and M2), 50% fructose/50% glycerol (M3 and M4), or 100%glycerol (M5 and M6). In the media used in Example 7, the ammoniumnitrate of typical MK102 growth medium was replaced with potassiumnitrate at either one-half (M1, M3, M5) or equal (M2, M4, M6) molarity.100 mL of growth medium was used in each test tray. Various parametersof the fungal biomass obtained from these tests are given in Table 6;results given for media without glycerol monostearate additive are theaverage of two test runs (except for medium M2), while results given formedium M2 and media with glycerol monostearate additive are for a singletest run.

TABLE 6 Time Initial Final Yield Waste Medium Additive (hours) pH pH (g)(mL) M1 None 72 3.25 1.41 20.751 17 GS 72 3.25 1.40 20.550 32 M2 None 723.25 3.15 50.304 1 None 48 3.25 2.88 32.67 0 GS 72 3.25 2.67 44.77 3 M3None 72 3.25 1.72 20.19 43 GS 72 3.25 1.74 21.055 15 M4 None 68 3.252.25 38.427 8 GS 72 3.25 1.89 35.03 12 M5 None 72 3.25 2.76 24.602 31 GS72 3.25 1.91 25.416 12 M6 None 72 3.25 5.21 20.293 38 GS 72 3.25 3.6521.576 30 Control None 72 3.25 4.61 24.924 32 GS 72 3.25 3.24 25.724 22

As Table 5 shows, culture M2 without glycerol monostearate additive over72 hours produced the highest yield, while culture M2 without glycerolmonostearate additive over 48 hours outperformed control cultures over72 hours.

Example 8

This Example illustrates a process for making fungal biomats using bothan AMC process and a conventional liquid surface fermentation (LSF)process.

All components of M2 medium as defined in Table 7 below (on a basis of120 liters of total medium), except for fructose, were added to aboilermaker in amounts sufficient to provide 80 liters of medium, andthe medium was brought to a boil. 10 liters of the boiling medium waspumped into each of eight separate pots. Fructose was added to each ofthese separate pots in varying amounts to provide two pots containingeach of four fructose concentrations (7.5%, 10%, 15%, and 20% w/v,respectively corresponding to molar carbon-to-nitrogen ratios in themedium of 8.24, 10.99, 16.48, and 21.98). Each pot of medium wasintermittently stirred until the fructose was fully dissolved, whereuponthe pot was covered with a lid and sealed with plastic wrap. Each potwas allowed to cool overnight to room temperature. The following day,the pH of the medium in each pot was adjusted to pH 3.5 with phosphoricacid. Fungal inoculum was then added to each pot in an amount of 5% v/v.One pot at each fructose concentration was mixed using a high-speeddisperser (HSD) at 5,000 rpm, with 0.4% w/v of xanthan gum added duringmixing. From each of the eight pots of medium, 2 liters of medium werepoured into each of five separate flat trays having a surface area of0.25 m². These 40 total trays were then placed on racks in a chambermaintained at a temperature of 31° C. and 88% relative humidity, and thefungal organism was allowed to grow for 96 hours under these conditions.

TABLE 7 Ingredient Amount Potassium nitrate 756 g Ammonium chloride813.6 g Urea 410.7 g Calcium chloride 159 g Magnesium sulfateheptahydrate 120 g Monopotassium phosphate 480 g Trace EDTA 48 mLFructose 9.000 kg (for 7.5 wt %) 12.000 kg (for 10 wt %) 18.000 kg (for15 wt %) 24.000 kg (for 20 wt %) Yeast extract 180 g Water 120 L

Example 9

This Example illustrates the effects on raw biomat thickness of carbonconcentration and/or carbon-to-nitrogen ratio in both AMCs andconventional LSF media.

The biomats produced in Example 8 were removed from the trays. Thethickness of each mat was measured at three separate points: on an edgeof the mat, in the center of the mat, and at a non-central interiorportion of the mat. This yielded a total of fifteen raw mat thicknessmeasurements for each of the eight medium types, i.e. 120 thicknessmeasurements in total. The results of these raw mat thicknessmeasurements are illustrated in FIG. 8.

As FIG. 8 illustrates, samples grown on AMCs displayed a trend ofincreasing thickness with increasing fructose (i.e. carbon)concentration. Samples grown on LSF media displayed an increase inthickness as fructose concentration increased from 7.5% to 10%, but thena decrease in thickness with increasing fructose concentration such thatthe lowest thickness was observed at the highest (20%) fructoseconcentration.

Example 10

This Example illustrates the effects on area yield and biomat density ofcarbon concentration and/or carbon-to-nitrogen ratio in both AMCs andconventional LSF media.

Using a knife, each of the 40 biomats produced in Example 8 was cut intoquarters, yielding a total of 20 mat specimens for each of the eightdifferent medium types; of these 20 specimens for each medium type, tworandomly selected specimens were placed in freezer bags and frozen forlater microscopy testing, while the remaining 18 specimens were boiledin water for 30 minutes and then soaked in deionized water at 70° C.,with intermittent stirring, for an additional 30 minutes. Of the 18boiled specimens for each medium type, four were dehydrated at 160° F.for 23 hours and then weighed. The average area yield (i.e. dry mass ofbiomat per area of fermentation tray) of these four specimens for eachof the medium types is illustrated in FIG. 9, and the average drydensity for these specimens is illustrated in FIG. 10.

As FIG. 9 illustrates, there are notable differences in area yieldbetween biomats grown on AMCs and those grown on conventional LSF media.Most strikingly, at all fructose concentrations, and especially thosehigher than 7.5%, area yield is significantly greater for biomats grownon AMCs than for those grown on LSF media. Additionally, while LSF matshave no discernible trend of yield with fructose concentration(suggesting that conditions other than carbon concentration and/orcarbon-to-nitrogen ratio play a greater role in area yield for LSFprocesses), for AMC mats there is an obvious trend in which yieldincreases with increasing fructose concentration up to about 15%, thendecreases slightly as fructose concentration is further increased to20%. This finding suggests that area yield, like raw mat thickness, canbe effectively controlled by controlling the carbon concentration and/orcarbon-to-nitrogen ratio of the growth medium. These trends are furtherillustrated in FIG. 10, in which the density of both AMC and LSF matsdoes not appear to increase or decrease predictably with fructoseconcentration, although, interestingly, whatever trends exist appear tobe the same for both AMC and LSF mats.

Example 11

This Example illustrates the effects of carbon concentration and/orcarbon-to-nitrogen ratio on the tensile strength and strain at break ofboiled AMC- and LSF-grown biomats.

Of the 18 boiled specimens for each medium type produced in Example 10,four were cut into pieces for testing of their mechanical properties,particularly their tensile strength and strain at break. The averagetensile strength of these four specimens for each of the medium types isillustrated in FIG. 11, and the average strain at break for thesespecimens is illustrated in FIG. 12.

As FIG. 11 illustrates, biomats grown on AMCs display a trend ofincreasing tensile strength with increasing fructose (i.e. carbon)concentration, while biomats grown using LSF media had consistenttensile strengths substantially independent of fructose concentration.As a result of these trends, at low fructose concentrations, mats grownon AMCs generally have tensile strengths below those grown on LSF media,but as fructose concentration increases, this difference narrows, and atthe highest fructose concentrations the tensile strength of mats grownon AMCs overtakes that of mats grown on LSF media. This once againdemonstrates that mechanical and material properties of fungal biomatscan be effectively controlled by controlling the carbon concentrationand/or carbon-to-nitrogen ratio in AMCs on which the biomats are grown.

As FIG. 12 illustrates, there is no clear trend in strain at break as afunction of fructose concentration for either AMC-grown or LSF-grownbiomats. Interestingly, however, the strains at break of AMC-grown andLSF-grown biomats appear to be largely comparable at all fructoseconcentrations. Additionally, without wishing to be bound by anyparticular theory, the fact that both types of biomat have their loweststrain at break at the lowest fructose concentration (7.5%) but theirhighest strain at break at the next lowest concentration (10%) may beexplained by the phenomenon of autolysis of cellular structures as aresult of exhaustion of the primary carbon source; at very low carbonconcentrations and/or carbon-to-nitrogen ratios, this autolysis may besignificant enough to result in wholesale degradation and thus weakeningat the entire mat, whereas a slightly lesser degree of autolysis at aslightly higher fructose concentration may provide just enough autolysisto allow for greater freedom of movement of fungal filaments understrain without compromising the structures to such an extent as toresult in total material failure.

Example 12

This Example illustrates the effects of carbon concentration and/orcarbon-to-nitrogen ratio on nutritional content in both AMC-grown andLSF-grown fungal biomats.

Of the 18 boiled specimens for each medium type produced in Example 10,two were chopped into small pieces and frozen in 50 mL conical tubes forcompositional analysis (protein, moisture, fat, ash, and carbohydrates).The average contents in these samples of ash (after combustion),carbohydrates, crude fat, and protein is illustrated in FIGS. 13Athrough 13D, respectively.

As FIGS. 13A through 13D illustrate, the nutritional compositions ofAMC-grown and LSF-grown biomats generally follow similar trends. Forboth types of mat, a general decrease in ash, fat, and protein contentsas fructose (i.e. carbon) concentration increases is observed, exceptfor possible slight increases in ash, and for AMC-grown mats in fat, atthe highest fructose concentrations (15% to 20%). The opposite trend isobserved with respect to carbohydrate content, which increases markedlyin both AMC- and LSF-grown mats as fructose concentration increases.Without wishing to be bound by any particular theory, the presentinventors believe this increase in carbohydrate content is the cause forthe positive trend in tensile strength with increasing fructoseconcentration that was observed in AMC-grown mats in Example 11, thoughwhy this same trend was not also observed with respect to LSF-grown matsis unclear.

Additionally, without wishing to be bound by any particular theory, itis believed that the boiling of the mats used in this Example accountsfor the largely similar protein contents of the AMC- and LSF-grown mats,as opposed to the marked differences observed in Example 3.Specifically, the boiling of the mats prior to assaying likely resultsin a significant fraction of the additional protein in the AMC-grownmats being washed away or otherwise lost to the water used for the boil.

Example 13

This Example illustrates a process for making AMCs for fungal biomatgrowth using various aeration and mixing techniques and devices.

Biomats were produced according to the procedure described in Example 8,except that the amount of fructose in each batch of growth medium was15% w/v and all batches were aerated and mixed with 0.4% w/v xanthan gumto create AMCs; in this Example, the variable that differentiated thevarious AMCs was the mixing device used to aerate the fermentationmedium to create the AMC. Specifically, three different mixing deviceswere used: a high-speed disperser (HSD) at 5,000 rpm, a high-shear mixer(HSM) at 10,000 rpm, and a KitchenAid kitchen mixer with a whiskattachment at a speed setting of 9 out of 10. AMCs made with the kitchenmixer were prepared in smaller batches (2 liters or less) due to thelimited volume of the mixing vessel.

Example 14

This Example illustrates the effects on raw biomat thickness and biomatarea yield and density of the mixing technique and device used toprepare the AMCs on which the biomats were grown.

The thickness of the biomats produced in Example 13 was measuredaccording to the procedure described in Example 9, and the area yieldand density of the mats was measured according to the proceduredescribed in Example 10. The results of the raw mat thicknessmeasurements are illustrated in FIG. 14, and the results of the areayield and density measurements are illustrated in FIGS. 15A and 15B,respectively.

As FIG. 14 illustrates, the thicknesses of all mat samples prepared inthis Example were largely similar. The only statistically significantdifference in thickness can be observed between mats grown on HSD AMCsand those grown on HSM AMCs; the HSD AMCs produced the thickest mats,while the HSM AMCs produced the thinnest mats. All samples hadstatistically similar area yields and mass densities. Without wishing tobe bound by any particular theory, it is believed that the device ortechniques used to aerate the fermentation medium to produce the AMC isnot as crucial to the thickness, yield, or density of the resultingbiomat as the ability of the medium itself to support a biomat on theliquid-air interface.

Example 15

This Example illustrates the effects of the mixing technique/device usedto prepare the AMCs on which fungal biomats are grown on the tensilestrength and strain at break of the resulting boiled biomats.

The tensile strength and strain at break of the biomats produced inExample 13 was measured according to the procedure described in Example11. The average tensile strength of the tested mats is illustrated inFIG. 16, and the average strain at break for these specimens isillustrated in FIG. 17.

As FIGS. 16 and 17 illustrate, mats produced from each of the threetypes of AMC (HSD, kitchen mixer with whisk attachment, and HSM) werelargely similar in their material and mechanical properties. However,one notable relationship can be observed in comparing the two figures:there is generally an inverse relationship between the tensile strengthand the strain at break for any particular mixing technique/device; matsproduced from HSM AMCs had the highest strain at break but the lowesttensile strength, while mats produced from HSD AMCs had the highesttensile strength but the lowest strain at break.

Example 16

This Example illustrates a process for making AMCs for fungal biomatgrowth using various stabilizers, surfactants, and thickeners.

Biomats were produced according to the procedure described in Example 8,except that the amount of fructose in each batch of growth medium was15% w/v and all batches were aerated using a high-shear mixer at 10,000rpm; in this Example, the variable that differentiated the various AMCswas the gum or other thickener or stabilizer mixed during aeration toform the AMC. Specifically, six AMCs were prepared, respectivelycontaining as stabilizer/thickener 0.4% w/v xanthan gum, 1.5% w/vcarboxymethyl cellulose (CMC), 1% w/v konjac root, 1.5% w/v guar gum,1.5% w/v arabic gum, and 1% w/v tara gum.

Qualitative assessment of the six types of AMCs and the biomats producedthereon revealed notable differences. A thickener of 0.4% w/v xanthangum formed a medium-viscosity liquid that upon aeration formed a highlystable AMC with a large volume fraction of trapped air. A thickener of1.5% w/v CMC formed only a semi-stable foam on the surface of thefermentation medium (i.e. without trapped air in the bulk of the liquidmedium); biomats grew unevenly and thinly on this substrate. A thickenerof 1% w/v konjac root formed a more stable foam to a greater depth inthe liquid medium relative to CMC, but foam formation was stillincomplete, and slow dissolution of the konjac led to a low-viscositysubstrate that produced inconsistent biomats (and, in the case of twotrays, failure to grow any biomat at all). A thickener of 1.5% w/v guargum dissolved slowly at first, resulting in an initially low-viscositysubstrate that thickened so substantially as to become nearly gel-like;biomats grown on this substrate were consistently thick and relativelydry, and had high bending rigidity. A thickener of 1.5% w/v arabic gumfailed to result in a stable foam; of the four trays using this AMC, twoyielded no biomat and the other two yielded only very thin mats. Athickener of 1% w/v tara gum formed a highly viscous and stable AMC thatconsistently yielded very thick mats with notably light and “fluffy”fungal hyphae.

Example 17

This Example illustrates the effects on raw biomat thickness and biomatarea yield and density of the thickener used to prepare the AMCs onwhich the biomats were grown.

The thickness of the biomats produced in Example 16 was measuredaccording to the procedure described in Example 9, and the area yieldand density of the mats was measured according to the proceduredescribed in Example 10. The results of the raw mat thicknessmeasurements are illustrated in FIG. 18, and the results of the areayield and density measurements are illustrated in FIGS. 19A and 19B,respectively.

As FIG. 18 illustrates, the thickness of biomats was greatly affected bythe thickener used to produce the AMC on which the mats were grown.High-thickness mats were obtained from AMCs containing xanthan gum, guargum, or tara gum, all of which were medium- or high-viscosity AMCs;without wishing to be bound by any particular theory, it is hypothesizedthat fungal biomat growth is most effectively promoted when the fungusis physically supported on the air-medium interface. As FIG. 19Aillustrates, area yields followed a similar trend as mat thickness. AsFIG. 19B illustrates, mat density was generally fairly stable andindependent of the thickener used, except for mats grown on the tara gumAMC, which were notably less dense than mats grown on other AMCs.

Example 18

This Example illustrates the effects of the thickener used to preparethe AMCs on which fungal biomats are grown on the tensile strength andstrain at break of the resulting boiled biomats.

The tensile strength and strain at break of the biomats produced inExample 16 was measured according to the procedure described in Example11. The average tensile strength of the tested mats is illustrated inFIG. 20, and the average strain at break for these specimens isillustrated in FIG. 21.

As FIG. 20 illustrates, the tensile strength of boiled biomats wasfairly consistent across all thickeners used. Two outliers in thisregard are the mats grown on a guar gum AMC, which had notably lowertensile strength than the other mats, and the mats grown on an arabicgum AMC, which had notably higher tensile strength than the other mats;without wishing to be bound by any particular theory, it is hypothesizedthat the relatively high tensile strength of the latter is due to thethinness of these mats. It was also observed that in addition to havinglower tensile strength, mats produced on guar gum AMCs were subjectivelymore brittle than other mats, possibly due to drying more during matgrowth. As FIG. 21 illustrates, strain at break is again fairlyconsistent across all thickeners used, but it is observed that there isa negative correlation between mat density and strain at break; withoutwishing to be bound by any particular theory, it is believed that matsof lower density have greater interior void space and thus a lowerdegree of entanglement or interconnection between fungal filaments,allowing for greater motion of filaments relative to each other when astress is applied.

Example 19

This Example illustrates the effects of the thickener used to preparethe AMCs on which fungal biomats are grown on the tensile strength andstrain at break of the resulting boiled biomats, and in particular theeffect of a combined xanthan gum/CMC thickener as compared to xanthangum alone.

Biomats were produced according to the procedure described in Example 8,except that the amount of fructose in each batch of growth medium was15% w/v and all batches were aerated using a high-speed disperser at5,000 rpm; in this Example, the variable that differentiated the AMCswas that half of the AMC samples (nine of 18) contained only 0.4% w/vxanthan gum, while the other half contained both 0.4% w/v xanthan gumand 0.5% w/v CMC (both added during aeration/mixing until fullydissolved). It was observed that the addition of both CMC and xanthangum resulted in a more viscous AMC than using xanthan gum alone.

The tensile strength and strain at break of the biomats produced wasmeasured according to the procedure described in Example 11. The resultsare given in Table 8.

TABLE 8 Thickener Strain at break Tensile strength Sample ID (all % w/v)(%) (kPa) 1 Xanthan gum only 20.031 250 2 Xanthan gum only 18.476 234 3Xanthan gum only 19.628 353 4 Xanthan gum only 21.679 148 5 Xanthan gumonly 12.968 116 6 Xanthan gum only 20.813 210 7 Xanthan gum only 18.519148 8 Xanthan gum only 21.510 268 9 Xanthan gum only 17.462 246 10Xanthan gum + CMC 41.818 293 11 Xanthan gum + CMC 42.970 313 12 Xanthangum + CMC 45.560 285 13 Xanthan gum + CMC 41.722 249 14 Xanthan gum +CMC 40.814 292 15 Xanthan gum + CMC 40.211 215 16 Xanthan gum + CMC45.951 248 17 Xanthan gum + CMC 45.507 244 18 Xanthan gum + CMC 25.665212 Average Xanthan gum only 19.010 219 Average Xanthan gum + CMC 41.135261

As the results given in Table 8 indicate, addition of CMC in addition toxanthan gum resulted in improvements in the strength of the biomat(average 116% improvement in strain at break and 19% improvement intensile strength). This allows for more forceful or energy-intensivepost-processing steps, e.g. to transform the biomat into a textile orstructural material, without risking breakage, rupture, or tear of thebiomat.

Example 20

This Example illustrates significant morphological differences betweenbiomats grown on AMCs and those grown on conventional liquid surfacefermentation media.

5 μm cross-sections of the mats grown on the 15 wt % fructose media(both AMC and LSF) of Example 8 were taken and stained, then examined byvisible light microscopy to examine differences in morphologicalstructure between such samples. Photomicrographs of the mat grown on theLSF medium are shown in FIGS. 22A through 22D, and photomicrographs ofthe mat grown on the AMC medium are shown in FIGS. 23A through 23D.

Comparison of the photomicrographs of FIGS. 22A through 23D reveals somestriking, and important, differences in the morphology of the matsobtained. The mat grown on the conventional LSF medium has a morehomogeneous morphology, with a gradual decrease in filament density fromthe medium side (FIG. 22B and top of FIG. 22A) to the hyphal side (FIG.22D and bottom of FIG. 22A). By contrast, the mat grown on the AMC showsthree very clearly observable morphological layers: a layer of verydense filaments on the medium side (FIG. 23B and top of FIG. 23A), asomewhat less dense layer on the hyphal side (FIG. 23D and bottom ofFIG. 23A), and, between these layers in the interior of the mat, a layerof relatively sparse filament growth and significant void space (FIG.23C and middle of FIG. 23A).

Without wishing to be bound by any particular theory, it is believedthat the layered morphology of biomats grown on AMCs according to thepresent invention can confer several advantages because the differentmorphologies of layers have different properties. By way of firstnon-limiting example, after harvesting of biomats, one can “shave” orotherwise selectively remove or separate one or more layers, e.g. adense medium-side layer as illustrated in FIG. 23B, from the biomat andthereby obtain two or more fungal materials having differentmorphologies, suitable for producing two or more different products(e.g. foodstuffs having different nutritional profiles, foodstuffs ortextiles having different textural properties, structural materials ortextiles having different mechanical properties, or a combination ofthese), from a single biomat production run. By way of secondnon-limiting example, the relative paucity of filaments in the interiorportion of the mat may reduce the degree to which filaments areentangled with each other and therefore allow a greater degree ofmovement of filaments or layers of the biomat relative to each other,which in turn may improve the mechanical characteristics (e.g. tensilestrength or strain at break) of the biomat as a whole.

Example 21

This Example illustrates the effect of the stabilizer content of an AMCon the overrun and drainage rate of the AMC, and in turn the effect ofthese parameters on biomat yield.

Four samples of a fructose-based fermentation medium were prepared andaerated to form an AMC; the samples were identical except that varyingamounts of xanthan gum were added to each sample to stabilize the AMC.The pH of each AMC was adjusted to 3.25. The density of each mediumprior to aeration was measured as 1.174 g/mL, and the overrun (i.e. theincrease in volume of the AMC relative to the volume of fermentationmedium used) was measured immediately after AMC preparation by measuringthe density of the AMC and comparing this to the density of the originalfermentation medium. The drainage rate (i.e. the volume of free liquidgenerated under the foam per unit time) was recorded one hour after AMCpreparation. The viscosity of the AMC was measured at 25° C. two hoursafter AMC preparation. Subsequently, 1750 g of each medium sample wasinoculated with a filamentous fungus inoculum and incubated for 72 hoursat 27° C. and 85% relative humidity, and the yield of the resultingbiomats was recorded. Results are given in Table 9.

TABLE 9 Xanthan Area yield (g/m²) % AMC density Overrun Drainage rateViscosity wt % Wet Dry solids (g/mL) (%) (mL/hr) (cP) 0.3 1120 295 26.220.446 62.01 15.0 11250 0.4 1400 335 24.00 0.402 65.76 7.5 10950 0.5 1370351 25.70 0.438 62.69 5.0 7650 0.6 1530 411 26.80 0.413 64.82 1.5 6550

As Table 9 shows, increasing stabilizer content in the AMC results indecreased drainage rate (i.e. increased foam stability) and decreasedviscosity. In turn, these material characteristics of the AMC arestrongly associated with an increase in the area yield of dry biomatproduced.

The invention illustratively disclosed herein suitably may be practicedin the absence of any element which is not specifically disclosedherein. It is apparent to those skilled in the art, however, that manychanges, variations, modifications, other uses, and applications of theinvention are possible, and also changes, variations, modifications,other uses, and applications which do not depart from the spirit andscope of the invention are deemed to be covered by the invention, whichis limited only by the claims which follow.

The foregoing discussion of the invention has been presented forpurposes of illustration and description. The foregoing is not intendedto limit the invention to the form or forms disclosed herein. In theforegoing Detailed Description of the Invention, for example, variousfeatures of the invention are grouped together in one or moreembodiments for the purpose of streamlining the disclosure. The featuresof the embodiments of the invention may be combined in alternateembodiments other than those discussed above. This method of disclosureis not to be interpreted as reflecting an intention that the claimedinvention requires more features than are expressly recited in eachclaim. Rather, as the following claims reflect, inventive aspects lie inless than all features of a single foregoing disclosed embodiment. Thus,the following claims are hereby incorporated into this DetailedDescription of the Invention, with each claim standing on its own as aseparate preferred embodiment of the invention.

Moreover, though the description of the invention has includeddescription of one or more embodiments and certain variations andmodifications, other variations, combinations, and modifications arewithin the scope of the invention, e.g. as may be within the skill andknowledge of those in the art, after understanding the presentdisclosure. It is intended to obtain rights which include alternativeembodiments to the extent permitted, including alternate,interchangeable, and/or equivalent structures, functions, ranges, orsteps to those claimed, whether or not such alternate, interchangeable,and/or equivalent structures, functions, ranges, or steps are disclosedherein, and without intending to publicly dedicate any patentablesubject matter.

The invention claimed is:
 1. A filamentous fungal biomat having a drydensity of at least about 0.20 g/cm³ and a tensile strength of at leastabout 255 kPa, produced by a method comprising: (a) aerating afermentation medium to provide an air-medium colloid (AMC); and (b)culturing a filamentous fungus in or on the AMC to form a biomass of thefilamentous fungus in the form of a coherent mat.
 2. The biomat of claim1, further comprising a stabilizer.
 3. The biomat of claim 1, furthercomprising a food-grade or food-safe additive.
 4. The biomat of claim 1,having at least one of the following properties: (a) a thickness of atleast about 1.75 mm; (b) a mass of at least about 295 grams per squaremeter of a top surface area of the AMC; and (c) a carbohydrate contentof at least about 47 wt % when dry.
 5. The biomat of claim 1, whereinthe AMC further comprises an inoculum of the filamentous fungus.
 6. Thebiomat of claim 1, wherein the method further comprises inoculating theAMC with an inoculum of the filamentous fungus.
 7. The biomat of claim1, wherein the AMC further omprises a stabilizer.
 8. The biomat of claim7, wherein the stabilizer is selected from the group consisting of apolysaccharide gum, an anionic surfactant, a cationic surfactant,ceteareth 20, cellulose, diacetyl tartaric esters of mono- anddiglycerides (DATEM), a diglyceride, an emulsifying wax, glycerolmonostearate, a lecithin, a monoglyceride, a mustard, a non-ionicsurfactant, a soap, a sodium phosphate, sodium stearoyl lactylate, azwitterionic surfactant, a saponin, a starch, a modified starch, a plantprotein surfactant, an animal protein surfactant, microparticulates,silica, and combinations and mixtures thereof.
 9. The biomat of claim 8,wherein the stabilizer comprises xanthan gum.
 10. The biomat of claim 7,wherein a mass ratio of the fermentation medium to the stabilizer in theAMC is between about 100:1 and about 1,000:1.
 11. The biomat of claim10, wherein the mass ratio is between about 166:1 and about 500:1. 12.The biomat of claim 1, wherein a volume fraction of air in the AMC isbetween about 0.05 and about 0.95.
 13. The biomat of claim 12, whereinthe volume fraction of air in the AMC is between about 0.3 and about0.7.
 14. The biomat of claim 1, wherein the AMC is a foam that is stableover at least about 1 day.
 15. The biomat of claim 14, wherein the foamis stable over at least about 3 days.
 16. The biomat of claim 1, whereinthe filamentous fungus belongs to an order selected from the groupconsisting of Ustilaginales, Russulales, Polyporales, Agaricales,Pezizales, and Hypocreales.
 17. The biomat of claim 1, wherein thefilamentous fungus belongs to a family selected from the groupconsisting of Ustilaginaceae, Hericiaceae, Polyporaceae, Grifolaceae,Lyophyllaceae, Strophariaceae, Lycoperdaceae, Agaricaceae, Pleurotaceae,Physalacriaceae, Omphalotaceae, Tuberaceae, Morchellaceae,Sparassidaceae, Nectriaceae, and Cordycipitaceae.
 18. The biomat ofclaim 1, wherein the filamentous fungus belongs to a species selectedfrom the group consisting of Ustilago esculenta, Hericulum erinaceus,Polyporous squamosus, Grifola fondosa, Hypsizygus marmoreus, Hypsizygusulmarius, Calocybe gambosa, Pholiota nameko, Calvatia gigantea, Agaricusbisporus, Stropharia rugosoannulata, Hypholoma lateritium, Pleurotuseryngii, Pleurotus ostreatus, Tuber borchii, Morchella esculenta,Morchella conica, Morchella importuna, Sparassis crispa, Fusariumvenenatum, MK7 ATCC Accession Deposit No. PTA-10698, Disciotis venosa,and Cordyceps militaris.
 19. The biomat of claim 1, wherein the methodfurther comprises, prior to or during step (b), adding a food-grade orfood-safe additive to the AMC.
 20. A foodstuff comprising the biomat ofclaim
 1. 21. A structural material comprising the biomat of claim
 1. 22.A textile material comprising the biomat of claim 1.